Braking control device for vehicle

ABSTRACT

An electric motor is controlled based on a target energization amount calculated based on an operation amount of a braking operation member. Based on the operation amount, it is determined whether or not an inertia compensation control for compensating for the influence of the inertia of a brake actuator is necessary. When the inertia compensation control is determined to be necessary, an inertia compensation energization amount compensating for the influence of the inertia of the brake actuator is calculated using a time-series pattern set in advance based on the maximum response of the brake actuator. Using the inertia compensation energization amount, the target energization amount is calculated. The vehicle brake control device causes an electric motor to generate a braking torque and appropriately compensates for the influence of the inertia of the entire device including the inertia of the electric motor.

TECHNICAL FIELD

The present invention relates to a vehicle brake control device.

BACKGROUND ART

Hitherto, there has been known a vehicle brake control device configuredto generate a braking torque by an electric motor. In the device of thistype, typically, an indication current (target current) is calculatedbased on an operation amount of a driver-operated braking operationmember of the vehicle, and the electric motor is controlled based on theindication current. Then, a braking torque that depends on the operationof the braking operation member is applied to the wheels.

In the device of this type, due to influences of the inertia (inertiamoment, inertia mass) of the entire device including the inertia of theelectric motor, particularly in a case of abrupt braking (upon rapidincrease of braking torque) or the like, a response delay of the brakingtorque (a delay of rise thereof) may occur in acceleration during whichthe rotation speed of the electric motor is increased (e.g., when theelectric motor is started) and an overshoot of the braking torque mayoccur in deceleration during which the rotation speed of the electricmotor is decreased (e.g., when the electric motor is intended to bestopped). Therefore, particularly, at abrupt braking, it is desired tocompensate for the influences of the inertia, that is, to improveresponsiveness (rising performance) of the braking torque duringacceleration of the electric motor and to suppress the overshoot of thebraking torque during deceleration of the electric motor (improve theconvergence).

As to how to cope with this problem, for example, Japanese PatentApplication Laid-open No. 2002-225690 describes as follows. That is,based on a map in which indication currents and target motor rotationangles are co-related, a target motor rotation angle corresponding tothe calculated indication current is determined, and a target motorrotation angular acceleration is calculated by subjecting the targetmotor rotation angle to the second-order differentiation. Based on thetarget motor rotation angular acceleration, an inertia compensationcurrent for compensating for the influences of the inertia of the entiredevice is calculated. In this case, the inertia compensation current iscalculated to be a positive value during acceleration of the electricmotor, while the inertia compensation current is calculated to be anegative value during deceleration of the electric motor. This inertiacompensation current is added to the indication current, to therebydetermine a compensated indication current (target current). In thismanner, the compensated indication current is calculated to be slightlylarger than the indication current when the electric motor is started,thereby being capable of improving the responsiveness of the brakingtorque. The compensated indication current is calculated to be slightlysmaller than the indication current when the electric motor is intendedto be stopped, thereby being capable of suppressing the overshoot of thebraking torque.

In addition, Japanese Patent Application Laid-open No. 2002-225690 alsodescribes providing a “gradient limitation” against the indicationcurrent for performing stable control when the indication currentexceeds the capacity of the electric motor.

SUMMARY OF INVENTION

By the way, as described in the above literature, in the case where theinertia compensation current is calculated based on the target motorrotation angular acceleration calculated based on the indicationcurrent, if the gradient limitation is provided against the indicationcurrent, the target motor rotation angular acceleration cannot becorrectly calculated, which is obtained by subjecting the target motorrotation angle obtained based on the indication current to thesecond-order differentiation. For example, if the indication current islimited to a predetermined gradient limit value, the target motorrotation angular acceleration that corresponds to the second derivativevalue of the indication current is maintained at “zero (0)”. As aresult, it may be difficult to provide an appropriate (highly precise)compensation for the above-mentioned influences of the inertia.

A description is now made of this matter with reference to FIG. 15. Inthe example shown in FIG. 15 in which the electric motor starts up at atime t0, an indication current is limited to a predetermined gradientlimit value in a period between “a time point after a short timeduration from the time t0” and “a time t1 at which a supposed indicationcurrent (see the solid line) and the indication current under thegradient limitation (see the dashed line) intersect”. In this case, therotation speed of the electric motor is increased for the short timeduration elapsed from the time t0 (thus, a positive target motorrotation angular acceleration is generated), the rotation speed of theelectric motor is decreased for a very short time duration elapsed fromthe time t1 (thus, a negative target motor rotation angular accelerationis generated), and the rotation speed of the electric motor remainsunchanged for other time durations (thus, the target motor rotationangular acceleration is maintained at zero (0)). In other words, asshown in FIG. 15, a positive inertia compensation current is generatedfor the short time duration elapsed from the time t0, a negative inertiacompensation current is generated for the very short time durationelapsed from the time t1, and the inertia compensation current ismaintained at zero (0) for the other time durations.

Therefore, improving the responsiveness of the braking torque duringacceleration of the electric motor is achieved insufficiently andsuppressing the overshoot of the braking torque during deceleration ofthe electric motor is also achieved insufficiently. This will request afurther adequate compensation for the influences of the inertia.

The present invention has been made for coping with the above-mentionedproblems, and has an object to provide a vehicle brake control deviceconfigured to generate a braking torque by an electric motor and capableof appropriately compensating for influences of an inertia of the entiredevice including an inertia of the electric motor.

A vehicle brake control device according to one embodiment of thepresent invention includes: operation amount acquisition means (BPA) foracquiring an operation amount (Bpa) of a driver-operated brakingoperation member (BP) of a vehicle; braking means (BRK) for causing anelectric motor (MTR) to generate a braking torque to a wheel (WHL) ofthe vehicle; and control means (CTL) for calculating a targetenergization amount (Imt) based on the operation amount (Bpa) andcontrolling the electric motor (MTR) based on the target energizationamount (Imt).

One feature of the present invention resides in that the control means(CTL) is configured to: determine, based on the operation amount (Bpa),whether or not inertia compensation control for compensating for aninfluence of an inertia (inertia moment, inertia mass) of the brakingmeans (BRK) is necessary; calculate, in a case where the inertiacompensation control is determined to be necessary (FLj←1 or FLk←1), aninertia compensation energization amount (Ijt, Ikt) for compensating forthe influence of the inertia of the braking means (BRK) based on atime-series pattern (CHj, CHk) that is set in advance based on a maximumresponse (e.g., step response) from the braking means (BRK); andcalculate the target energization amount (Imt) based on the inertiacompensation energization amount (Ijt, Ikt).

More specifically, the control means (CTL) may be configured to:determine, based on the operation amount (Bpa), whether or not theinertia compensation control is necessary during acceleration of theelectric motor in which a rotation speed thereof increases; and use, ina case where the inertia compensation control during the acceleration isdetermined to be necessary (FLj←1), as the time-series pattern (CHj), afirst pattern in which the inertia compensation energization amount(Ijt) increases from zero at an increase gradient and thereafterdecreases to zero at a decrease gradient, the increase gradient beingset in advance based on an actual position change (e.g., actual rotationangular acceleration) of the electric motor (MTR) that occurs when astep input of the target energization amount (Imt) is performed to theelectric motor (MTR), the decrease gradient being set in advance to bemore gentle than the increase gradient.

Likewise, the control means (CTL) may be configured to: determine, basedon the operation amount (Bpa), whether or not the inertia compensationcontrol is necessary during deceleration of the electric motor in whichthe rotation speed thereof decreases; and use, in a case where theinertia compensation control during the deceleration is determined to benecessary (FLk←1), as the time-series pattern (CHk), a second pattern inwhich the inertia compensation energization amount (Ikt) decreases fromzero at a decrease gradient and thereafter increases to zero at anincrease gradient, the decrease gradient being set in advance based onan actual position change (e.g., actual rotation angular acceleration)of the electric motor (MTR) that occurs when a step input of the targetenergization amount (Imt) is performed to the electric motor (MTR), theincrease gradient being set in advance to be more gentle than thedecrease gradient.

In order to ensure the responsiveness of the braking torque duringacceleration (particularly, upon start-up) of the electric motor, it isimportant to improve the initial movement (from the rest state to thestart-up state) of the electric motor by compensating for the influencesof the static friction of the bearings and the like of the electricmotor and also by compensating for the influences of the inertia of theentire device. With the above-mentioned configuration, afterdetermination of necessity for the inertia compensation control duringacceleration, it is possible to output an inertia compensationenergization amount having the preset first time-series pattern(waveform that changes with time). Therefore, the influences of theinertia of the entire device including the electric motor, and thestatic friction of, for example, the bearings are compensated, and hencethe responsiveness of the braking torque at the initial movement of theelectric motor can efficiently be improved.

Likewise, also during deceleration of the electric motor (when theelectric motor shifts to its stopped state from the moving state), it isimportant to compensate for the inertia of the electric motor at aninitial stage of the deceleration. With the above-mentionedconfiguration, after determination of necessity for the inertiacompensation control during deceleration, it is possible to output aninertia compensation energization amount having the preset secondtime-series pattern (waveform that changes with time). Therefore, thedeceleration of the electric motor is increased immediately after theelectric motor begins to decelerate, and hence the overshoot of thebraking torque can efficiently be suppressed. In summary, with theabove-mentioned configuration, it is possible to efficiently andproperly compensate for the influences of the inertia of the entiredevice including the inertia of the electric motor.

In the above-mentioned brake control device, it is preferred that thecontrol means (CTL) be configured to maintain the inertia compensationenergization amount (Ijt) at zero in a case where the electric motor(MTR) is in motion immediately before the inertia compensation controlduring acceleration is determined to be necessary (FLj←1). In otherwords, in a case where the electric motor has already been in rotationat a time when the inertia compensation control during acceleration isdetermined to be necessary, the inertia compensation control duringacceleration is not executed.

In general, the necessity for improving the responsiveness of thebraking torque during acceleration of the electric motor is significantwhen the electric motor is at rest before start of the braking control.With the above-mentioned configuration, the inertia compensation controlduring acceleration is executed only in a case where the electric motoris at rest when the inertia compensation control during acceleration isdetermined to be necessary. Therefore, an occurrence of an unnecessaryexecution of the inertia compensation control during acceleration issuppressed, and hence the control reliability can be improved.

In addition, in the above-mentioned brake control device, it ispreferred that the control means (CTL) be configured to calculate theinertia compensation energization amount (Ikt) based on the secondpattern (CHk) instead of the first pattern (CHj) in a case where theinertia compensation control during deceleration is determined to benecessary (FLk←1) in a period during which the inertia compensationenergization amount (Ijt) is calculated based on the first pattern(CHj).

In this manner, in a case where a driver stops abrupt braking during theexecution of the inertia compensation control during accelerationstarted by the driver's operation for the abrupt braking, the executionof the inertia compensation control during acceleration can be stoppedimmediately and instead an immediate execution of the inertiacompensation control during deceleration can be started. Thus, it ispossible to reliably suppress the overshoot of the braking torque.

In addition, in the above-mentioned brake control device, it ispreferred that the control means (CTL) be configured to maintain theinertia compensation energization amount (Ikt) at zero in a case wherethe inertia compensation control during deceleration is determined to benecessary (FLk←1) in a state in which the inertia compensation controlduring acceleration is not determined to be necessary.

In general, in a case where the inertia compensation control is notnecessary upon start-up of the electric motor, the probability ofnecessity for the inertia compensation control is also low duringdeceleration. With the above-mentioned configuration, only in a casewhere the inertia compensation control during acceleration is necessaryupon start-up of the electric motor, the inertia compensation controlduring deceleration is executed. Thus, an occurrence of an unnecessaryexecution of the inertia compensation control during deceleration issuppressed, and hence the control reliability can be improved.

Another vehicle brake control device according to the present inventionincludes: operation amount acquisition means (BPA) for acquiring anoperation amount (Bpa) of a driver-operated braking operation member(BP) of a vehicle; braking means (BRK) for causing an electric motor(MTR) to generate a braking torque to a wheel (WHL) of the vehicle; andcontrol means (CTL) for calculating a target energization amount (Imt)based on the operation amount (Bpa) and controlling the electric motor(MTR) based on the target energization amount (Imt).

One feature of the present invention resides in that the control means(CTL) is configured to: calculate an inertia compensation energizationamount (Ijt, Ikt) for compensating for an influence of an inertia of thebraking means (BRK) based on a delay element (DLY) having a timeconstant (τm) indicating a response from the braking means (BRK) and theoperation amount (Bpa); and calculate the target energization amount(Imt) based on the inertia compensation energization amount (Ijt, Ikt).

In order to ensure the responsiveness of the braking torque duringacceleration (particularly, upon start-up) of the electric motor, it isimportant to improve the initial movement (from the rest state to thestart-up state) of the electric motor by compensating for the influencesof the static friction of the bearings and the like of the electricmotor and also by compensating for the influences of the inertia of theentire device. With the above-mentioned configuration, the actualresponse of the braking means is indicated based on the “delay elementusing the time constant (a parameter indicating the quickness of theresponse from the delay element)” instead of the above-mentioned“gradient limitation”, and hence the inertia compensation currentimmediately after the electric motor is brought into acceleration cancorrectly be calculated (see FIG. 10 to be described later). Therefore,the influences of the inertia of the entire device including theelectric motor, and the static friction of, for example, the bearingsand the like are compensated, and hence the responsiveness of thebraking torque at the initial movement of the electric motor canefficiently be improved.

Likewise, also during deceleration of the electric motor (when theelectric motor shifts to its stopped state from the moving state), it isimportant to compensate for the inertia of the electric motor at aninitial stage of the deceleration. With the above-mentionedconfiguration, the actual response of the braking means is indicatedbased on the “delay element using the time constant” instead of theabove-mentioned “gradient limitation”, and hence the inertiacompensation current immediately after the electric motor is broughtinto deceleration can correctly be calculated (see FIG. 10 to bedescribed later). Therefore, the deceleration of the electric motor isincreased immediately after the electric motor starts to decelerate, andhence the overshoot of the braking torque can efficiently be suppressed.In summary, with the above-mentioned configuration, it is possible toefficiently and properly compensate for the influences of the inertia ofthe entire device including the inertia of the electric motor.

In the above-mentioned brake control device, it is preferred that thecontrol means (CTL) be configured to: calculate a processing value (fBp,fFb, fMk) based on the delay element (DLY) and the operation amount(Bpa); calculate an acceleration equivalent value (ddfBp, ddfFb, ddfMk)by subjecting the processing value (fBp, fFb, fMk) to second-orderdifferentiation; and calculate the inertia compensation energizationamount (Ijt, Ikt) based on the acceleration equivalent value (ddfBp,ddfFb, ddfMk).

The torque that compensates for the inertia of the entire device(particularly, the inertia of the electric motor) is in proportion tothe rotation angular acceleration of the electric motor. In view of thisfact, in order to perform the inertia compensation in an adequatemanner, it is important to calculate the inertia compensationenergization amount based on the rotation angular acceleration of theelectric motor (or an equivalent value of the same dimension). Theabove-mentioned configuration is based on those findings.

In the above-mentioned brake control device, it is preferred todetermine the time constant (τm) to have a relatively larger value asthe operation amount (Bpa) becomes larger. In this manner, the timeconstant is set to a small value at a stage in which the operationamount is small, that is, immediately after the electric motor starts toaccelerate (upon start-up of the electric motor), and the time constantis set to a large value at a stage in which the operation amount islarge, that is, during deceleration of the electric motor. As a result,the responsiveness of the braking torque upon start-up of the electricmotor can be ensured, and the acceleration equivalent value that is usedfor calculating the inertia compensation energization amount canproperly be calculated during deceleration of the electric motor.

In the above-mentioned brake control device, it is preferred that thecontrol means (CTL) be configured to: calculate a first kind of theinertia compensation energization amount (Ijt) for increasing the targetenergization amount (Imt) based on a first time-series pattern (CHj) setin advance in a case where the acceleration equivalent value (ddfBp,ddfFb, ddfMk) exceeds a first predetermined acceleration (ddb1); andcalculate a second kind of the inertia compensation energization amount(Ikt) for decreasing the target energization amount (Imt) based on asecond time-series pattern (CHk) set in advance in a case where theacceleration equivalent value (ddfBp, ddfFb, ddfMk) is less than asecond predetermined acceleration (ddb2).

In order to enhance the effects of the inertia compensation control, itis important to compensate for the initial acceleration in the motion.With the above-mentioned configuration, the proper inertia compensationenergization amount can be calculated based on the preset time-seriespattern so as to compensate for the inertia at the initial stage ofstart of the acceleration or deceleration motion of the electric motor.Moreover, the start of the inertia compensation control can bedetermined based on the acceleration equivalent value. It is to be notedthat the time-series pattern whose characteristic depends on the inertiaof the electric motor can be found by way of experiments or other means.

It is preferred that the above-mentioned brake control device furtherinclude energization amount acquisition means (IMA) for acquiring anactual energization amount (Ima) to the electric motor (MTR), and thatthe control means (CTL) be configured to: calculate, in a case where theacceleration equivalent value (ddfBp, ddfFb, ddfMk) exceeds a firstpredetermined acceleration (ddb1), a first kind of the inertiacompensation energization amount (Ijt) for increasing the targetenergization amount (Imt) based on a first time-series pattern (CHj) setin advance, and acquire time-series data (Jdk) that corresponds to thefirst pattern (CHj) based on the actual energization amount (Ima)acquired in correspondence to the first inertia compensationenergization amount (Ijt); and calculate a second kind of the inertiacompensation energization amount (Ikt) for decreasing the targetenergization amount (Imt) based on the time-series data (Jdk) in a casewhere the acceleration equivalent value (ddfBp, ddfFb, ddfMk) is lessthan a second predetermined acceleration (ddb2).

Depending on conditions including a power supply voltage, the actualenergization amount may be insufficient relative to the targetenergization amount. With the above-mentioned configuration, based onthe actual energization amount during acceleration of the electricmotor, the inertia compensation energization amount during decelerationof the electric motor (i.e., target energization amount) is determined.As a result, the proper inertia compensation control suitable forsituations including the power supply voltage can be executed.

In the above-mentioned brake control device, it is preferred that thecontrol means (CTL) be configured to: determine, based on the operationamount (Bpa), whether or not the braking operation member (BP) is in anacceleration state in which an operation speed thereof increases; andavoid executing calculation processing that uses the delay element (DLY)in a case where the acceleration state is determined (FLa=1), andexecute the calculation processing that uses the delay element (DLY) ina case where the acceleration state is not determined (FLa=0).

In general, calculation processing of a state amount by using the delayelement is disadvantageous in view of the responsiveness. With theabove-mentioned configuration, when the braking operation is inacceleration (when the operation speed of the braking operation memberis being increased), that is, when the responsiveness of the brakingtorque is in high request, the calculation processing that uses thedelay element is inhibited, thereby ensuring the responsiveness of thebraking torque.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a vehicle that isequipped with a brake control device according to one embodiment of thepresent invention.

FIG. 2 is a diagram illustrating a configuration of braking means (brakeactuator) (Z portion) that is illustrated in FIG. 1.

FIG. 3 is a functional block diagram illustrating the braking means(brake controller) that is illustrated in FIG. 1.

FIG. 4 is a functional block diagram illustrating an inertiacompensation control block that is illustrated in FIG. 3 according to afirst embodiment of the present invention.

FIG. 5 is a graph showing a maximum response from the braking means(brake actuator).

FIG. 6 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to asecond embodiment of the present invention.

FIG. 7 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to athird embodiment of the present invention.

FIG. 8 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to afourth embodiment of the present invention.

FIG. 9 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to afifth embodiment of the present invention.

FIG. 10 is a graph showing operations and effects that are inassociation with calculation processing using a delay element.

FIG. 11 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to asixth embodiment of the present invention.

FIG. 12 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to aseventh embodiment of the present invention.

FIG. 13 is a graph showing a maximum response from the braking means(brake actuator).

FIG. 14 is a functional block diagram illustrating the inertiacompensation control block that is illustrated in FIG. 3 according to aneighth embodiment of the present invention.

FIG. 15 is a time chart illustrating an example of a calculated resultof an inertia compensation current when a related-art brake controldevice provides a gradient limitation against an indication current.

DESCRIPTION OF EMBODIMENTS

Now, a vehicle brake control device according to embodiments of thepresent invention is described with reference to the drawings.

<Overall Configuration of Vehicle Equipped with Vehicle Brake ControlDevice of the Present Invention>

As illustrated in FIG. 1, this vehicle is equipped with a brakingoperation member (e.g., brake pedal) BP that is used by a driver fordecelerating the vehicle, braking means (brake actuator) BRK by which abraking torque of each wheel is adjusted to generate a braking forcetherefor, an electronic control unit ECU for controlling the BRK, and abattery BAT as a power source for supplying electric power to the BRK,the ECU, and the like.

In addition, this vehicle includes braking operation amount acquisitionmeans (such as stroke sensor or leg-force sensor) BPA for detecting anoperation amount Bpa of the BP, steering angle detection means SAA fordetecting a steering angle Saa of a steering wheel SW operated by thedriver, yaw rate detection means YRA for detecting a yaw rate Yra of thevehicle, longitudinal acceleration detection means GXA for detecting avehicle longitudinal acceleration Gxa, lateral acceleration detectionmeans GYA for detecting a vehicle lateral acceleration Gya, and wheelspeed detection means VWA for detecting a rotation speed (wheel speed)Vwa of each wheel WHL.

The braking means BRK is equipped with an electric motor MTR (not shown)and the braking torque of the wheel WHL is controlled by the MTR. Inaddition, the BRK includes pushing force detection means (e.g., axialforce sensor) FBA for detecting a pushing force Fba of a friction memberto push a rotating member, energization amount detection means (e.g.,current sensor) IMA for detecting an energization amount (e.g., currentvalue) Ima to the MTR, and position detection means (e.g., rotationangle sensor) MKA for detecting the position (e.g., rotation angle) Mkaof the MTR.

The above-mentioned signals (such as Bpa) that are detected by thevarious detection means are subject to noise removal (reduction) filter(e.g., low-pass filter) processing and then are supplied to the ECU. Inthe ECU, arithmetic processing for the brake control related to thepresent invention is executed. That is to say, control means CTL to bedetailed later is programmed in the ECU, and a target energizationamount (e.g., target current value or target duty ratio) Imt forcontrolling the electric motor MTR is calculated based on the Bpa andthe like. In addition, based on the Vwa, the Yra, and the like, in theECU, arithmetic processing is executed for, for example, anti-skidcontrol (ABS), traction control (TCS), and vehicle stabilization control(ESC) that are known.

<Configuration of Braking Means (Brake Actuator) BRK>

In the brake control device according to the present invention, theelectric motor MTR generates and adjusts the braking torque of the wheelWHL.

As illustrated in FIG. 2 that is an enlarged view of the Z portion ofFIG. 1, the braking means BRK includes a brake caliper CPR, a rotatingmember KTB, a friction member MSB, the electric motor MTR, driving meansDRV, a reduction mechanism GSK, a rotation/linear motion conversionmechanism KTH, the pushing force acquisition means FBA, the positiondetection means MKA, and the energization amount acquisition means IMA.

Similarly to the related-art braking device, the brake actuator BRKincludes the brake caliper CPR that is known and the friction members(e.g., brake pads) MSB. The MSBs are pushed against the rotating member(e.g., brake rotor) KTB that is known to cause frictional forces,thereby generating a braking torque at the wheel WHL.

In the driving means (driving circuit of the electric motor MTR) DRV,based on the target energization amount (target value) Imt, anenergization amount (ultimately, current value) to the electric motorMTR is controlled. In detail, in the driving circuit DRV, a bridgecircuit that uses power transistors (e.g., MOS-FETs) is formed, and thepower transistors are driven based on the target energization amount Imtto control the output of the electric motor MTR.

The output (output torque) of the electric motor MTR is transmitted, byway of the reduction mechanism (e.g., gear sets) GSK, to therotation/linear motion conversion mechanism KTH. Then, the KTH convertsa rotation motion into a linear motion, and the linear motion urges thefriction members (brake pads) MSB onto the rotating member (brake disc)KTB. The KTB is fixed to the wheel WHL, and the friction between the MSBand the KTB generates the braking torque at the wheel WHL in anadjustable fashion. As the rotation/linear motion conversion mechanismKTH, a sliding screw (e.g., trapezoidal screw) that uses “sliding” forpower transmission (sliding transmission) or a ball screw that uses“rolling” for power transmission (rolling transmission) is available.

The motor driving circuit DRV includes the energization amountacquisition means (e.g., current sensor) IMA for detecting the actualenergization amount (e.g., actual current flowing to the electric motor)Ima. In addition, the electric motor MTR is equipped with the positiondetection means (e.g., angle sensor) MKA for detecting its position(e.g., rotation angle) Mka. Further, the pushing force acquisition means(e.g., force sensor) Fba is provided for acquiring (detecting) the force(actual pushing force) Fba with which the friction member MSB actuallypushes the rotating member KTB.

In FIG. 2, a so-called disc type braking device (disc brake) isillustrated as an exemplary configuration of the braking means BRK, butthe braking means BRK may be in the form of a drum type braking device(drum brake). In the case of the drum brake, the friction member MSB isa brake shoe and the rotating member KTB is a brake drum. Similarly, theforce with which the brake shoe pushes the brake drum (pushing force) iscontrolled by the electric motor MTR. As the electric motor MTR, adevice that generates a torque by rotation motion is exemplified, but alinear motor is available that generates a force by linear motion.

<Overall Configuration of Control Means CTL>

As illustrated in FIG. 3, the control means CTL that is illustrated inFIG. 1 includes a target pushing-force calculation block FBT, anindication energization amount calculation block IST, a pushing-forcefeedback control block IPT, an inertia compensation control block INR,and an energization amount adjusting calculation block IMT. The controlmeans CTL is programmed in the electronic control unit ECU.

An operation amount Bpa of the braking operation member BP (e.g., brakepedal) is acquired by the braking operation amount acquisition meansBPA. The operation amount of the braking operation member (brakingoperation amount) Bpa is calculated based on at least one of anoperation force of the braking operation member (e.g., brake pedalforce) operated by the driver and a displacement amount (e.g., brakepedal stroke) thereof. The Bpa is subject to calculation processingusing a low-pass filter or the like for noise component removal(reduction).

In the target pushing-force calculation block FBT, a predeterminedtarget pushing-force calculation characteristic (calculation map) CHfbis used for calculating a target pushing-force Fbt based on theoperation amount Bpa. The “pushing-force” is a force with which thefriction member (e.g., brake pad) MSB pushes the rotating member (e.g.,brake disc) KTB in the braking means (brake actuator) BRK. The targetpushing-force Fbt is a target value of the pushing-force.

The indication energization amount calculation block IST calculates, byusing predetermined calculation maps CHs1 and CHs2, an indicationenergization amount Ist based on the target pushing-force Fbt. Theindication energization amount Ist is a target value of the energizationamount to the electric motor MTR in order to drive the electric motorMTR of the braking means BRK for achieving the target pushing-force Fbt.Taking into consideration of the hysteresis of the brake actuator, thecalculation map (calculation characteristics for indication energizationamount) has the two characteristics CHs1 and CHs2. The characteristic(first indication energization amount calculation characteristic) CHs1is for coping with an increase of the pushing-force, while thecharacteristic (second indication energization amount calculationcharacteristic) CHs2 is for coping with a decrease of the pushing-force.For this reason, the characteristic CHs1 is set so as to output arelatively large indication energization amount Ist as compared to thecharacteristic CHs2.

As used herein, the energization amount is a state amount (variable) forcontrolling an output torque of the electric motor MTR. Due to the factthat the torque output from the electric motor MTR is almost inproportion to a current supplied thereto, a current target value of theelectric motor is available as a target value of the energizationamount. In addition, when a voltage supplied to the electric motor MTRis increased, the resultant current is increased, and hence a supplyvoltage value is available as the target energization amount. Moreover,a duty ratio in pulse width modulation (PWM) makes it possible to adjustthe supply voltage value, and hence this duty ratio is available as theenergization amount.

In the pushing-force feedback control block IPT, a pushing-forcefeedback energization amount Ipt is calculated based on the targetpushing-force (target value) Fbt and the actual pushing-force (actualvalue) Fba. The indication energization amount Ist is calculated as avalue that corresponds to the target pushing-force Fbt, but anefficiency variation of the brake actuator may cause an error(steady-state error) between the target pushing-force Fbt and the actualpushing-force Fba. The pushing-force feedback energization amount Ipt iscalculated and determined to decrease the above-mentioned error(steady-state error) based on a deviation (pushing-force deviation) ΔFbbetween the target pushing-force Fbt and the actual pushing-force Fbaand a calculation characteristic (calculation map) CHp.

In the inertia compensation control block INR, the influence of theinertia (inertia moment in rotation motion or inertia mass in linearmotion) of the BRK (particularly, electric motor MTR) is compensated. Inthe inertia compensation control block INR, target values Ijt and Ikt ofthe energization amount for compensating for the influence of theinertia (inertia moment or inertia mass) of the BRK are calculated. Itis necessary to improve a responsiveness of pushing-force generation ina case where the motion (rotation motion) of the electric motor isbrought into acceleration from a state in which the electric motor is atrest or in motion at low speed. In such a case, the correspondingduring-acceleration inertia compensation energization amount Ijt iscalculated. The Ijt is a target value of the energization amount of thecontrol during acceleration in the inertia compensation control.

In addition, in a case where the electric motor is brought intodeceleration to stop from the state in which the electric motor is inmotion (rotation motion), it is also necessary to improve theconvergence by suppressing the overshoot of the pushing force. To copewith such a case, a during-deceleration inertia compensationenergization amount Ikt is calculated. The Ikt is a target value of theenergization amount of the control during deceleration in the inertiacompensation control. As used herein, the Ijt is a value (a positivevalue added to the Ist) for increasing the energization amount to theelectric motor, while the Ikt is a value (a negative value added to theIst) for decreasing the energization amount to the electric motor.

Then, in the energization amount adjusting calculation block IMT, theindication energization amount Ist is adjusted by the pushing-forcefeedback energization amount Ipt and the inertia compensationenergization amount Ijt (during acceleration) or the inertiacompensation energization amount Ikt (during deceleration), therebycalculating the target energization amount Imt. In detail, theindication energization amount Ist is added with the feedbackenergization amount Ipt and the inertia compensation energization amountIjt or Ikt, and the resultant sum is calculated as the targetenergization amount Imt. The target energization amount Imt is anultimate target value of the energization amount for controlling theoutput of the electric motor MTR.

<Configuration of Inertia Compensation Control Block of FirstEmbodiment>

With reference to FIG. 4, the inertia compensation control block INRaccording to a first embodiment of the present invention is described.As illustrated in FIG. 4, in this inertia compensation control blockINR, inertia compensation control is executed for improving theresponsiveness of the pushing force which is caused by the inertia ofthe MTR or the like (the overall inertia of the BRK including theinertia of the MTR) and the convergence. The inertia compensationcontrol block INR includes a control necessity determination calculationblock FLG for determining whether or not the inertia compensationcontrol is necessary, an inertia compensation energization amountcalculation block IJK for calculating a target energization amount forthe inertia compensation control, and a selection calculation block SNT.

In the control necessity determination calculation block FLG, it isdetermined whether or not executing the inertia compensation control isnecessary. The control necessity determination calculation block FLGincludes a during-acceleration determination calculation block FLJ fordetermining the necessity during acceleration of the electric motor(e.g., when the electric motor starts up and increases its speed) and aduring-deceleration determination calculation block FLK for determiningthe necessity during deceleration of the electric motor (e.g., when theelectric motor is intended to be stopped). The control necessitydetermination calculation block FLG outputs, as a determination result,a necessity determination flag FLj (during acceleration) or FLk (duringdeceleration). “0” of each of the necessity determination flags FLj andFLk represents that the inertia compensation control is unnecessary(unnecessary state), while “1” represents that the inertia compensationcontrol is necessary (necessary state).

The control necessity determination calculation block FLG includes anoperation speed calculation block DBP, the during-accelerationdetermination calculation block FLJ, and the during-decelerationdetermination calculation block FLK.

At first, in the operation speed calculation block DBP, based on theoperation amount Bpa of the braking operation member BP, an operationspeed dBp thereof is calculated. The operation speed dBp is calculatedby differentiating the Bpa.

In the during-acceleration determination calculation block FLJ, it isdetermined based on the operation speed dBp which of the “necessarystate (state for which executing the control is necessary)” and the“unnecessary state (state for which executing the control isunnecessary)” the inertia compensation control is in during accelerationof the electric motor (e.g., when the rotation speed of the electricmotor increases). The result of the determination is output as thenecessity determination flag (control flag) FLj. “0” and “1” of thenecessity determination flag FLj correspond to the “unnecessary state”and the “necessary state”, respectively. Regarding the necessitydetermination of the during-acceleration inertia compensation control,at a time point when the dBp exceeds a predetermined operation speed(predetermined value) db1, the during-acceleration necessitydetermination flag FLj is switched from “0 (unnecessary state)” to “1(necessary state)” (FLj←1) in accordance with the calculation map CFLj.Thereafter, the necessity determination flag FLj is switched from “1” to“0” (FLj←0) at a time point when the dBp is less than a predeterminedoperation speed (predetermined value) db2. It is to be noted that theFLj is set to be “0” as an initial value in a case where the brakingoperation is not performed.

Further, in the necessity determination of the during-accelerationinertia compensation control, the operation amount Bpa of the brakingoperation member is available in addition to the operation speed dBp. Insuch a case, at a time point when the Bpa exceeds a predeterminedoperation amount (predetermined value) bp1 and the dBp exceeds thepredetermined operation speed (predetermined value) db1, the necessitydetermination flag FLj is switched from “0” to “1”. The use of thecondition of Bpa>dp1 as a determination criteria can compensate for theinfluences of noise and the like in the dBp, thereby enabling a reliabledetermination.

In the during-deceleration determination calculation block FLK, it isdetermined based on the dBp which of the “necessary state (state forwhich executing the control is necessary)” and the “unnecessary state(state for which executing the control is unnecessary)” the inertiacompensation control is in during deceleration of the electric motor(e.g., when the rotation speed of the electric motor decreases). Theresult of the determination is output as the necessity determinationflag (control flag) FLk. “0” and “1” of the necessity determination flagFLk correspond to the “unnecessary state” and the “necessary state”,respectively. Regarding the necessity determination of theduring-deceleration inertia compensation control, at a time point whenthe dBp that is equal to or more than a predetermined operation speed(predetermined value) db3 is changed to be less than a predeterminedoperation speed (predetermined value) db4 (<db3), the necessitydetermination flag FLk is switched from “0 (unnecessary state)” to “1(necessary state)” (FLk←1) in accordance with the calculation map CFLk.Thereafter, for the prevention of frequent repetition of theduring-acceleration control and the during-deceleration control thatdepends on the dBp, it is possible to set the predetermined operationspeed db3 in the during-deceleration control to be less than thepredetermined operation speed db1 in the during-acceleration control. Itis to be noted that the FLk is set to be “0” as an initial value in acase where the braking operation is not performed.

Information on the necessity determination flags FLj and FLk for theinertia compensation control is fed from the control necessitydetermination calculation block FLG to the inertia compensationenergization amount calculation block IJK.

In the inertia compensation energization amount calculation block IJK,the inertia compensation energization amount (target value) iscalculated in a case where the inertia compensation control isdetermined to be necessary (FLj=1 or FLk=1) in the FLG. The inertiacompensation energization amount calculation block IJK includes aduring-acceleration energization amount calculation block IJT forcalculating the inertia compensation energization amount Ijt duringacceleration of the electric motor (e.g., when the electric motor startsup and increases its speed) and a during-deceleration energizationamount calculation block IKT for calculating the inertia compensationenergization amount Ikt during deceleration of the electric motor (e.g.,when the electric motor is intended to be stopped).

In the during-acceleration energization amount calculation block IJT,the during-acceleration inertia compensation energization amount (firstinertia compensation energization amount) Ijt is calculated based on thenecessity determination flag FLj and the during-acceleration calculationcharacteristic (calculation map corresponding to the first pattern) CHj.The during-acceleration calculation characteristic CHj is pre-stored inthe ECU as the characteristic (calculation map) of the Ijt relative toan elapsed time T since the during-acceleration inertia compensationcontrol is determined to be necessary. The calculation characteristicCHj is set so that the Ijt increases abruptly from “0” to apredetermined energization amount (predetermined value) ij1 along withtime from the time T of “0” and thereafter decreases gently from thepredetermined energization amount (predetermined value) ij1 to “0” alongwith time. In detail, in the CHj, a time duration tup that is requiredfor the Ijt to increase from “0” to the predetermined energizationamount ij1 is set to be shorter than a time duration tdn that isrequired for the Ijt to decrease from the predetermined energizationamount ij1 to “0”.

As illustrated in FIG. 4 with broken lines, in a case where theenergization amount increases, it is possible to set the CHj so that theIjt, which has a “concave-down” characteristic, first increases abruptlyand thereafter increases gently. On the other hand, in a case where theenergization amount decreases, it is possible to set the CHj so that theIjt, which has a “concave-up” characteristic, first decreases abruptlyand thereafter decreases gently. Then, the time point when the necessitydetermination flag FLj is switched from “0 (unnecessary state)” to “1(necessary state)” is defined as an original time point (T=0) of theelapsed time in the CHj, and the inertia compensation energizationamount during acceleration of the electric motor (first inertiacompensation energization amount) Ijt is determined based on the elapsedtime T measured from the switched time point and the during-accelerationcalculation characteristic CHj. Even though the necessity determinationflag FLj is switched from “1” to “0” in the calculation of the Ijt, theduring-acceleration energization amount Ijt keeps being calculated overa continuation duration that is set in advance in the calculationcharacteristic CHj. It is to be noted that the Ijt is calculated as apositive value and is adjusted to increase the energization amount tothe electric motor MTR.

In the during-deceleration energization amount calculation block IKT,the during-deceleration inertia compensation energization amount (secondinertia compensation energization amount) Ikt is calculated based on thenecessity determination flag FLk and the during-deceleration calculationcharacteristic (calculation map corresponding to the second pattern)CHk. The during-deceleration calculation characteristic CHk ispre-stored in the ECU as the characteristic (calculation map) of the Iktrelative to an elapsed time T since the during-deceleration inertiacompensation control is determined to be necessary. The CHk is set sothat the Ikt decreases abruptly from “0” to a predetermined energizationamount (predetermined value) ik1 along with time from the time T of “0”and thereafter increases gently from the predetermined energizationamount (predetermined value) ik1 to “0” along with time. In detail, inthe CHk, a time duration tvp that is required for the Ikt to decreasefrom “0” to the predetermined energization amount ik1 is set to beshorter than a time duration ten that is required for the Ikt toincrease from the predetermined energization amount ik1 to “0”.

As illustrated in FIG. 4 with broken lines, in a case where theenergization amount decreases, it is possible to set the CHk so that theIkt, which has a “concave-up” characteristic, first decreases abruptlyand thereafter decreases gently. On the other hand, in a case where theenergization amount increases, it is possible to set the CHk so that theIkt, which has a “concave-down” characteristic, first increases abruptlyand thereafter increases gently. Then, the time point when the necessitydetermination flag FLk is switched from “0” to “1” is defined as anoriginal time point (T=0) of the elapsed time in the CHk, and theinertia compensation energization amount during deceleration of theelectric motor (second inertia compensation energization amount) Ikt isdetermined based on the elapsed time T measured from the switched timepoint and the during-deceleration calculation characteristic CHk. Eventhough the necessity determination flag FLk is switched from “1” to “0”in the calculation of the Ikt, the Ikt keeps being calculated over acontinuation duration that is set in advance in the calculationcharacteristic CHk. It is to be noted that the Ikt is calculated as anegative value and is adjusted to decrease the energization amount tothe electric motor MTR.

As used herein, the calculation characteristic CHj (first pattern) inthe during-acceleration inertia compensation control and the calculationcharacteristic CHk (second pattern) in the during-deceleration inertiacompensation control are determined based on the maximum response fromthe braking means (brake actuator) BRK. In response to the changing ofthe input (target energization amount) to the BRK, the resultant output(displacement of the electric motor) occurs with a delay. The maximumresponse from the BRK (the maximum achievable state of the BRK inresponse to the input) means a response from the MTR when providing astep input to the electric motor MTR (how the temporal change amount ofthe output changes in response to the temporal change amount of theinput. In other words, how the actual displacement (rotation angle) Mkaof the electric motor MTR changes when the MTR is supplied with apredetermined target energization amount Imt as a step input (in anincreasing direction from zero). As shown in FIG. 5, in a case where theelectric motor MTR is supplied with the (predetermined) targetenergization amount as a step input (thus, when the target value Mkt ofthe rotation angle is provided as a step input (of a predeterminedamount mks0)), the actual value (output) Mka of the rotation anglechanges to achieve the target value (input) Mkt (to follow the targetvalue with a delay). The CHj and the CHk are determined based on thechange of the Mka.

The torque that compensates for the inertia of the entire device(particularly, the inertia of the electric motor) is in proportion tothe rotation angular acceleration of the electric motor. Inconsideration of this fact, for achieving the inertia compensationproperly, the inertia compensation energization amount is calculatedbased on an actual acceleration (rotation angular acceleration) ddMka ofthe electric motor. For this reason, the acceleration (rotation angularacceleration) ddMka is calculated by subjecting the actual displacement(rotation angle) value Mka of the MTR to the second-orderdifferentiation, and the CHj and CHk are determined based on theresultant ddMka. For example, it is possible to set the first patternCHj and the second pattern CHk by multiplying the ddMka with acoefficient K (constant).

In the CHj, the increase gradient of the Ijt upon abrupt increasethereof (the gradient of the Ijt relative to time) is determined basedon the maximum value or the average value of the increase gradient ofthe ddMka (the gradient of the ddMka that increases relative to time)between a time t1 when the step input starts and a time t2 when therotation angular acceleration ddMka reaches its maximum value ddm1. Onthe other hand, the decrease gradient of the Ijt upon gentle decreasethereof (the gradient of the Ijt relative to time) is determined basedon the maximum value or the average value of the decrease gradient ofthe ddMka (the gradient of the ddMka that decreases relative to time)between the time t2 when the ddMka reaches its maximum value ddm1 and atime t3 when the ddMka reaches almost zero.

In addition, based on the ddMka at the maximum response (step response)(based on the change of ddMka between the times t1 and t2), in a casewhere the energization amount increases, it is possible to set the CHjso that the Ijt, which has a “concave-down” characteristic, firstincreases abruptly and thereafter increases gently. Similarly, based onthe ddMka at the maximum response (based on the change of ddMka betweenthe times t2 and t3), in a case where the energization amount decreases,it is possible to set the CHj so that the Ijt, which has a “concave-up”characteristic, first decreases abruptly and thereafter decreasesgently.

In the CHk, the decrease gradient of the Ikt upon abrupt decreasethereof (the gradient of the Ikt relative to time) is determined basedon the minimum value or the average value of the decrease gradient ofthe ddMka (the gradient of the ddMka that decreases relative to time)between a time t4 when the ddMka begins to decrease from zero and a timet5 when the ddMka reaches its minimum value ddm2. On the other hand, theincrease gradient of the Ikt upon gentle increase thereof (the gradientof the Ikt relative to time) is determined based on the maximum value orthe average value of the increase gradient of the ddMka (the gradient ofthe ddMka that increases relative to time) between the time t5 when theddMka reaches its minimum value ddm2 and a time t6 when the ddMkareturns to almost zero.

In addition, based on the ddMka at the maximum response (step response)(based on the change of ddMka between the times t4 and t5), in a casewhere the energization amount decreases, it is possible to set the CHkso that the Ikt, which has a “concave-up” characteristic, firstdecreases abruptly and thereafter decreases gently. Similarly, based onthe ddMka at the maximum response (based on the change of ddMka betweenthe times t5 and t6), in a case where the energization amount increases,it is possible to set the CHk so that the Ikt, which has a“concave-down” characteristic, first increases abruptly and thereafterincreases gently.

In a case where the electric motor MTR is in acceleration (particularly,when the MTR starts up), generating torque is required for overcomingthe frictions of the bearings of the MTR, and the like, while in a casewhere the electric motor MTR is in deceleration (particularly, when theMTR is stopping), the frictions acts on the MTR to be decelerated. Forthis reason, the absolute value of the during-acceleration predeterminedenergization amount (the first predetermined energization amount) ij1 isset to be larger than the absolute value of the during-decelerationpredetermined energization amount (the second predetermined energizationamount) (|ij1|>|ik1|).

In the selection calculation block SNT, one of the output of the inertiacompensation energization amount Ijt during acceleration of the electricmotor, the output of the inertia compensation energization amount Iktduring deceleration of the electric motor, and the output of controlstop (output of value “0”) is selected and output. In the selectioncalculation block SNT, in a case where the during-deceleration inertiacompensation energization amount Ikt (<0) is output while theduring-acceleration inertia compensation energization amount Ijt (>0) isbeing output, instead of the Ijt, the Ikt is capable of being outputwith priority. The inertia compensation control is performed based onthe time-series waveforms CHj, CHk that are preset by using, as atrigger, the determination of “necessary state” (necessity determinationflag). With the above-mentioned configuration, when the driver stops theabrupt braking, the during-acceleration inertia compensation control(calculation of the Ijt) is immediately stopped and is switched to theduring-deceleration inertia compensation control (calculation of theIkt). In this manner, it is possible to positively suppress theovershoot of the pushing-force.

In the control necessity determination calculation block FLg, it isdetermined whether or not the inertia compensation control is necessarybased on the operation speed dBp, but, instead of the operation speeddBp, it is possible to use a target pushing-force speed dFb obtained bydifferentiating the target pushing-force Fbt. In addition, in a casewhere the position (e.g., target rotation angle) Mkt of the electricmotor is employed as the target value, a target rotation speed dMkobtained by differentiating the target rotation angle Mkt can be usedfor the necessity determination. In other words, it is possible todetermine whether or not the inertia compensation control is necessarybased on the value (speed equivalent value) dBp that is equivalent tothe operation speed, and is obtained by differentiating the brakingoperation amount Bpa, the dFb, and the dMk.

<Configuration of Inertia Compensation Control Block of SecondEmbodiment>

Next, with reference to FIG. 6, the inertia compensation control blockINR according to a second embodiment of the present invention isdescribed. As illustrated in FIG. 6, this inertia compensation controlblock INR includes a control necessity determination calculation blockFLG, an inertia compensation energization amount calculation block IJK,and a selection calculation block SNT. The IJK and the SNT are the sameas those of the INR in the first embodiment illustrated in FIG. 4, andhence the detailed description thereof is omitted. Hereinafter, only thecontrol necessity determination calculation block FLG is described.

The control necessity determination calculation block FLG includes anoperation acceleration calculation block DDBP, a during-accelerationdetermination calculation block FLJ, and a during-decelerationdetermination calculation block FLK.

In the operation acceleration calculation block DDBP, based on theoperation amount Bpa of the braking operation member, an operationacceleration ddBp thereof is calculated. The operation acceleration ddBpis calculated by finding the second-order differentiation of the Bpa. Inother words, the operation amount Bpa is differentiated to calculate theoperation speed dBp and then the operation speed dBp is differentiated,to thereby calculate the operation acceleration ddBp.

In the during-acceleration determination calculation block FLJ, it isdetermined, based on the operation acceleration ddBp, when the inertiacompensation control is carried out during acceleration of the electricmotor MTR, which of the “necessary state (state for which executing thecontrol is necessary)” and the “unnecessary state (state for whichexecuting the control is unnecessary).” The result of the determinationis output as a necessity determination flag (control flag) FLj. “0” and“1” of the necessity determination flag FLj correspond to the“unnecessary state” and the “necessary state,” respectively. Inaccordance with a calculation map DFLj, at a time point when theoperation acceleration ddBp exceeds a first predetermined acceleration(predetermined value) ddb1 (>0), the during-acceleration necessitydetermination flag FLj is switched from “0 (unnecessary state)” to “1(necessary state)” (FLj←1). Thereafter, the FLj is switched from “1” to“0” (FLj←0) at a time point when the operation acceleration ddBp is lessthan a predetermined acceleration (predetermined value) ddb2 (<ddb1). Itis to be noted that while the FLj is set to be “0” as an initial valuein a case where the braking operation is not performed.

In the during-deceleration determination calculation block FLK, it isdetermined, based on the operation acceleration ddBp, when the inertiacompensation control is carried out during deceleration of the electricmotor MTR, which of the “necessary state (state for which executing thecontrol is necessary)” and the “unnecessary state (state for whichexecuting the control is unnecessary).” The result of the determinationis output as a necessity determination flag (control flag) FLk. “0” and“1” of the necessity determination flag FLk correspond to the“unnecessary state” and the “necessary state,” respectively. Inaccordance with a calculation map DFLk, at a time point when theoperation acceleration ddBp is less than a second predeterminedacceleration (predetermined value) ddb3 (<0), the during-decelerationnecessity determination flag FLk is switched from “0 (unnecessarystate)” to “1 (necessary state)” (FLk←1). Thereafter, FLk is switchedfrom “1” to “0” (FLk←0) at a time point when the operation accelerationddBp is equal to or more than a predetermined acceleration(predetermined value) ddb4 (>ddb3, <0). It is to be noted that the FLkis set to be “0” as an initial value in a case where the brakingoperation is not performed.

Similarly to the above-mentioned first embodiment (see FIG. 4), thenecessity determination flags FLj and FLk are fed to the inertiacompensation energization amount calculation block IJK (IJT and IKT) andinertia compensation energization amounts Ijt and Ikt are calculatedbased on a preset time-series patterns (calculation maps) CHj and CHk.

In the control necessity determination calculation block FLG, a delayelement calculation block DLY can be provided. In the delay elementcalculation block DLY, the operation amount Bpa is subject to a delayelement calculation processing, and it is possible to calculate theoperation acceleration ddfBp based on the resultant operation amountfBp. In the delay element calculation block DLY, the response (how theoutput changes in response to the input change) from the brake actuatorBRK (particularly, the electric motor MTR) is taken into considerationof a transfer function with the delay element. The term “delay element”used herein is an n-th order delay element (where “n” is an integer of“1” or more) and is, for example, the primary delay element.Specifically, the delay element calculation (e.g., the primary delaycalculation) is executed using a time constant τm that indicates theresponse from the brake actuator BRK. The response from the brakeactuator BRK is taken into consideration of the delay element, whichenables the proper inertia compensation control.

In the control necessity determination calculation block FLG, whether ornot the inertia compensation control is necessary is determined based onthe operation acceleration ddBp (or the operation acceleration ddfBpsubjected to the calculation processing with the above-mentioned delayelement). Alternatively, however, instead of the ddBp or ddfBp, it ispossible to employ a target pushing-force acceleration ddFb (or theddfFb subjected to the above-mentioned delay calculation processing)which is calculated by subjecting the target pushing-force Fbt (or thefFb obtained after the above-mentioned delay calculation processing) tothe second-order differentiation. In addition, in a case where, as atarget value, the position (e.g., target rotation angle) Mkt of theelectric motor is used, for the necessity determination, it is possibleto employ a target rotation acceleration ddMK (a ddfMk subjected to theabove-mentioned delay calculation processing) that is calculated bysubjecting the target rotation angle Mkt (or an fMk obtained after theabove-mentioned processing) to the second-order differentiation. Inother words, it is possible to determine the necessity of the inertiacompensation control based on a value that is equivalent to theacceleration of the braking operation (acceleration equivalent value)ddBp, ddFb, and ddMk, and is obtained by subjecting the brakingoperation amount Bpa to the second-order differentiation (or the ddfBp,ddfFb, and ddfMk obtained after the above-mentioned delay calculationprocessing).

It is to be noted that, in the above-mentioned INR of the firstembodiment (see FIG. 4), both the determination calculation (calculationof FLj) during acceleration of the electric motor and the determinationcalculation (calculation of FLk) during deceleration of the electricmotor are executed based on the operation speed (speed equivalent value)dBp or the like, while in the INR of the second embodiment (see FIG. 6),both the during-acceleration determination calculation (calculation ofFLj) and the during-deceleration determination calculation (calculationof the FLk) are executed based on the operation acceleration(acceleration equivalent value) ddBp or the like. In addition, thecontrol necessity determination calculation block FLG may include thecombination of the “the FLj calculation based on the dBp or the like”and “the FLk calculation based on the ddBp or the like”. Alternatively,the control necessity determination calculation block FLG may includethe combination of the “the FLj calculation based on the ddBp or thelike” and “the FLk calculation based on the dBp or the like”.

<Configuration of Inertia Compensation Control Block of ThirdEmbodiment>

Next, with reference to FIG. 7, the inertia compensation control blockINR according to a third example of the present invention is described.Even when the during-acceleration inertia compensation energizationamount Iji is output as a value in which the responsiveness of theelectric motor MTR is taken into consideration, the actual energizationamount to the electric motor MTR does not always match the target valuedepending on a condition of the power supply voltage (e.g., when avoltage drops). For example, in a case where the actual energizationamount is insufficient when the electric motor MTR starts up, if thepreset during-deceleration inertia compensation energization amount Iktis output, an insufficient pushing-force may be generated in the brakeactuator BRK. For this reason, in this embodiment, based on an actualenergization amount (e.g., current value) Ima that is acquired by theenergization amount acquisition means (e.g., current sensor) IMA, theduring-deceleration inertia compensation energization amount Ikt can becalculated.

As illustrated in FIG. 7, this inertia compensation control block INRincludes the control necessity determination calculation block FLG, theinertia compensation energization amount calculation block IJK, and theselection calculation block SNT. The FLG and the SNT are the same asthose in the first and second embodiments that are illustrated in FIG. 4and FIG. 6, respectively, and hence the detailed descriptions thereofare omitted. Hereinafter, only the inertia compensation energizationamount calculation block IJK is described.

The inertia compensation energization amount calculation block IJKincludes the during-acceleration energization amount calculation blockIJT and the during-deceleration energization amount calculation blockIKT. The during-acceleration energization amount calculation block IJTis the same as the INR of the first embodiment that is illustrated inFIG. 4 and thus the detailed description thereof is omitted.

The during-deceleration energization amount calculation block IKT isprovided with a data memory calculation block JDK for storing thetime-series data Jdk based on the actual energization amount Ima overthe period in which the Ijt is output. The actual energization amountIma is acquired by the energization amount acquisition means (e.g.,current sensor) IMA in correspondence to the during-acceleration inertiacompensation energization amount Ijt. The time-series data Jdk is storedin the data memory calculation block JDK, as the characteristics thatindicate the actual energization amount Ija corresponding to the Ijt,with respect to a lapse of time T. Then, based on the time-series dataJdk, the during-deceleration inertia compensation energization amountIkt is calculated.

In the during-deceleration energization amount calculation block IKT,first, the indication energization amount Ist and the feed-backenergization amount Ipt is removed (subtracted) from the actualenergization amount Ima, thereby calculating the actual energizationamount (actual value) Ija that corresponds to the during-accelerationinertia compensation energization amount (target value) Ijt. In otherwords, the energization amount Ija that corresponds to the Ijt iscalculated by removing a component resulted from the Ist and ancomponent resulted from the Ipt from the Ima. Then, the correspondingenergization amount Ija is multiplied by “−1” (inversion of sign) andfurther is multiplied by a coefficient k_ij, thereby calculating anenergization amount Ikb that is stored in the data memory calculationblock JDK.

In the data memory calculation block JDK, the memory energization amountIkb, that is stored as the time-series data set Jdk, is related to atime T that elapses from a time point (T=0) at which theduring-acceleration control necessity determination flag FLj istransferred from “0 (unnecessary state)” to “1 (necessary state)” (i.e.,a time elapse from the initiation of the during-acceleration inertiacompensation control). Further, the time-series data set Jdk based onthe actual energization amount Ima serves as a characteristic(calculation map) for calculating the Ikt. Base on the time T thatelapses from a time point (T=0) at which the during-deceleration controlnecessity determination flag FLk is transferred from “0 (unnecessarystate)” to “1 (necessary state)” and the Jdk, the during-decelerationinertia compensation energization amount Ikt is calculated.

While it is necessary to generate a torque for overcoming frictions atthe bearings and the like of the electric motor MTR during acceleration(particularly, initiation) thereof, due to the fact that such frictionsact on the MTR to decelerate during deceleration (when being intended tostopped), the coefficient k_ij may be set to be less than “1”.

In the above descriptions, the memory energization amount Ikb iscalculated every calculation period. Instead, it is possible tocalculate the characteristic Jdk by storing values of the Ima, Ist, andIpt that are related to the elapsed time T as time-series data sets, andusing those values. In other words, it is possible to determine thecharacteristic (calculation map) Jdk based on a calculation: thetime-series data set of Jdk=(−1)×(k_ij)×{(the time-series data set ofIma)−(the time series data set of Ist)−(the time series data set ofIpt)}.

In the INR of the third embodiment, the during-deceleration inertiacompensation control is executed based on the actual energization amountIma that is obtained in the execution of the during-acceleration inertiacompensation control, and hence an adequate execution of inertiacompensation control can be performed even when an error occurs betweenthe target value and the actual value which is affected by the powersupply and the like.

<Configuration of Inertia Compensation Control Block of FourthEmbodiment>

Next, with reference to FIG. 8, the inertia compensation control blockINR according to a fourth embodiment of the present invention isdescribed. In this embodiment, there is provided a control permissiondetermination calculation block FLH, and based on a determination resultof the FLH, it is possible to determine a selection condition (switchingamong the Ijt, the Ikt, and control stop) of the selection calculationblock SNT that is described in the INRs of the first to thirdembodiments (see FIG. 4, FIG. 6, and FIG. 7). The control permissiondetermination calculation block SNT is fed with the inertia compensationenergization amount Ijt or Ikt similar to that in each of the first tothird embodiments.

In the control permission determination calculation block FLH, it isdetermined whether an execution of the during-acceleration inertiacompensation control (i.e., calculating the Ijt) is “permitted (FLm=1)”or “prohibited (FLm=0)” based on the actual position (real position,e.g., the rotation angle of the electric motor) Mka that is acquired bythe position acquisition means (e.g., the rotation angle sensor of theelectric motor) MKA.

In the control permission determination calculation block FLH, based onthe real position Mka, a speed (rotation speed) dMka of the electricmotor MTR is calculated. If the rotation speed dMka of the electricmotor MTR is less than a predetermined speed (predetermined value) dm1,the control is permitted to be executed, resulting in outputting “1” asthe permission determination flag FLm. On the other hand, if therotation speed dMka of the electric motor MTR is equal to or greaterthan the predetermined speed (predetermined value) dm1, the control isprohibited to be executed, resulting in outputting “0” as the permissiondetermination flag FLm. Then, in the selection calculation block SNT, ina case where permission determination flag FLm is “0”, “0 (controlstop)” is selected, while in a case where the permission determinationflag FLm is “1”, the during-acceleration inertia compensationenergization amount Ijt is selected.

The permission determination of the inertia compensation control may beestablished based on whether or not the electric motor MTR is at restwith reference to the real position Mka. In a case where the electricmotor is at rest (whose rotation speed is zero), the control ispermitted to be executed, resulting in outputting “1” as the permissiondetermination flag FLm. On the other hand, in a case where the electricmotor is in motion (e.g., is in a rotation movement, generating arotation speed), the control is prohibited to be executed, resulting inoutputting “0” as the permission determination flag FLm. Then, in theselection calculation block SNT, in a case where the permissiondetermination flag FLm is “0”, “0 (control stop)” is selected, while ina case where the permission determination flag FLm is “1”, theduring-acceleration inertia compensation energization amount Ijt isselected.

Immediately before the determination of the above-mentionedduring-acceleration inertia compensation control is determined to benecessary (immediately before the FLj is switched from “0” to “1”), in acase where the rotation speed of the electric motor is high (dMka≧dm1)or in a case where the electric motor is already in motion (in rotationmovement) (dMka≠0), compensating for the inertia of the electric motoror the like is not in high necessity, which prohibits the execution ofthe inertia compensation control. The during-acceleration inertiacompensation control is executed only when the electric motor rotates atlow speed (dMka<dm1) or at rest (dMka=0), and hence the inertiacompensation control is executed with high reliability.

In the control permission determination calculation block FLH, based onthe actual position Mka that is acquired by the position acquisitionmeans MKA, it is determined whether executing the during-decelerationinertia compensation control (i.e., calculating the Ikt) is “permitted(FLn=1)” or “prohibited (FLn=0)”. Based on the actual speed Mka, thepeed (rotation speed) dMka of the electric motor is calculated. In acase where the actual rotation speed dMka of the electric motor MTR isequal or larger than the predetermined speed (predetermined value) dm1(dMka≧dm1), executing the control is permitted, resulting in outputting“1” as the permission determination flag FLn. On the other hand, in acase where the actual rotation speed dMka of the electric motor is lessthan the predetermined speed (predetermined value) dm1 (dMka<dm1),executing the control is prohibited, resulting in outputting “0” as thepermission determination flag FLn. Then, in the selection calculationblock SNT, in a case where the permission determination flag FLn is “0”,“0 (control stop)” is selected, while in a case where the permissiondetermination flag FLn is “1”, the during-deceleration inertiacompensation energization amount Ikt is selected.

It is possible for the during-deceleration inertia compensation controlto suppress the overshoot of the electric motor MTR. However, in a casewhere the electric motor is not in high speed motion, theduring-deceleration inertia compensation control is in low necessity,and hence the inertia compensation control is prohibited in a case wherethe rotation speed of the electric motor is low (in a case of dMka<dm1).

In addition, in the control permission determination calculation blockFLH, based on at least one of the energization amount (target value) Ijtof the during-acceleration inertia compensation control and thenecessity determination flag FLj, it is determined whether executing theduring-deceleration inertia compensation control (i.e., calculating theIkt) is “permitted (FLo=1)” or “prohibited (FLo=0)”. Prior to theabove-mentioned determination of the necessity of during-decelerationinertia compensation control (during-deceleration control), based onwhether or not the during-acceleration inertia compensation control(during-acceleration control) is executed, it is determined whether theduring-deceleration control is permitted or prohibited. In a case wherethe during-acceleration control is not executed, the determination is tobe “prohibited,” resulting in outputting “0” as a permissiondetermination flag FLo. On the other hand, in a case where theduring-acceleration control is executed, the determination is to be“prohibited,” resulting in outputting “1” as the permissiondetermination flag FLo. In the selection calculation block SNT, in acase where the permission determination flag FLo is “0 (prohibitedstate)”, “0 (control stop)” is selected, while in a case where thepermission determination flag FLo is “1 (permitted state)”, theduring-deceleration inertia compensation energization amount Ikt isselected.

In a case where the inertia compensation control is unnecessary duringacceleration of the electric motor MTR, during deceleration thereof, theof necessity is low. With the above-mentioned configuration, theduring-deceleration control is executed only when the “necessary state”is determined during acceleration, which can improve the inertiacompensation control reliability, thereby allowing execution of thecontrol with reliability.

Furthermore, in the selection calculation block SNT, even though theduring-acceleration energization amount Ijt is not reduced to as low as“0” (i.e., the during-acceleration inertia compensation control is notcompleted), in a case where the during-deceleration energization amountIkt is output, the Ijt is set to be “0”, which allows the selectioncalculation block SNT to output therefrom the during-decelerationenergization amount Ikt. Giving the Ikt a higher priority than the Ijtmakes it possible to adequately prevent the overshoot of the electricmotor MTR and a surplus pushing force in a case where a brakingoperation is made abruptly but the operation amount is small.

Now, regarding the inertia compensation control in the inertiacompensation control block INR, operation and effect that are common tothe first to fourth embodiments are described. The inertia compensationcontrol is a control for adjusting the energization amount (Ijt, Ikt)relative to the target energization amount Imt, the energization amount(Ijt, Ikt) corresponding to the force (torque) that is necessary for themoving parts (including the MTR) of the device having an inertia toaccelerate or decelerate. In detail, the energization amount iscompensated for (corrected) by increasing the target energization amountduring acceleration of the electric motor, while the energization amountis compensated for (corrected) by decreasing the target energizationamount during deceleration of the electric motor.

In order to ensure the responsiveness of the braking torque duringacceleration of the electric motor MTR (particularly, at itsinitiation), it is important to improve the start-up of the electricmotor MTR (motion initial stage from at rest) by compensating for theinfluences of the inertia of the electric motor MTR and static frictionsof the bearings and the like. According to the above-mentioned first tofourth embodiments, after the time point at which executing theduring-acceleration inertia compensation control is determined to benecessary, it is possible to output the inertia compensationenergization amount Ijt that is in the form of the first presettime-series pattern CHj. The CHj is set based on the maximum response(how the actual displacement Mka of the MTR changes in response to thechange of the step input of the target energization amount) of thebraking actuator BRK (particularly, the electric motor MTR). Thus, it ispossible to adequately compensate for the influences of the inertia ofthe BRK and to compensate for the influences of the static frictions ofthe bearings and the like of the electric motor MTR and the like,resulting in remarkable improvement of the responsiveness of the brakingtorque when the electric motor MTR begins to be in motion.

Likewise, during deceleration of the electric motor MTR (in the case ofthe transfer from motion state to rest state), it is also important tocompensate for the inertia at the initial stage of the deceleration ofthe electric motor MTR. According to the above-mentioned first to fourthembodiments, after the time point at which executing theduring-deceleration inertia compensation control is determined to benecessary, it is possible to output the inertia compensationenergization amount Ikt that is in the form of the second presettime-series pattern CHk. The CHk is set based on the maximum response(how the actual displacement Mka of the MTR changes in response to thechange of the step input of the target energization amount) of thebraking actuator BRK (particularly, the electric motor MTR). Thus, it ispossible to adequately compensate for the influences of the inertia ofthe BRK, resulting in an increase of the deceleration of the electricmotor MTR immediately after the electric motor MTR begins to decelerate,followed by a remarkable suppression of the overshoot of the brakingtorque. In summary, according to the first to fourth embodiments, it ispossible to effectively and adequately compensate for the influences ofthe inertia of the braking means BRK that includes the inertia of theelectric motor MTR.

<Configuration of Inertia Compensation Control Block of FifthEmbodiment>

With reference to FIG. 9, the inertia compensation control block INRaccording to a fifth embodiment of the present invention is described.For the preparation thereof, as detailed below, various codes aredefined. Each code affixed with “f” is a state amount (fMk or the like)which is obtained by subjecting its original state amount (Mkt or thelike) to calculation processing using the delay element with the timeconstant τm as described later and which is referred to as “processedvalue”. It is to be noted that the “original state amount (originalvalue)” is a value before the calculation processing (delay processing)using the delay element and is referred to as “unprocessed value”. Inaddition, each code affixed with “d” is a state amount (dfMk or thelike) which is obtained by subjecting the original state amount (fMk orthe like) to first-order differentiation and corresponds to speed. Thisstate amount (value obtained by subjecting the “original state amount”to first-order differentiation) is referred to as “speed value” or“speed equivalent value”. A state amount (dfMk or the like) which isobtained by subjecting the processed value (fMk or the like) tofirst-order differentiation is referred to as “processed speed value(post-process speed value)” or “processed speed equivalent value(post-process speed equivalent value)”. Moreover, each code affixed with“dd” is a state amount (ddfMk or the like) which is obtained bysubjecting the original state amount (fMk or the like) to second-orderdifferentiation and corresponds to acceleration. This state amount(value obtained by subjecting the “original state amount” tosecond-order differentiation) is referred to as “acceleration value” or“acceleration equivalent value”. A state amount (ddfMk or the like)obtained by subjecting the processed value (fMk or the like) tosecond-order differentiation is referred to as “processed accelerationvalue (post-process acceleration value)” or “processed accelerationequivalent value (post-process acceleration equivalent value)”.

As illustrated in FIG. 9, in this inertia compensation control blockINR, an inertia compensation control is executed in order to improve theresponsiveness of the pushing force caused by the inertia of the MTR andthe like (the inertia of the entire BRK that includes the inertia of theMTR) and the convergence thereof. The inertia compensation control blockINR includes a target position calculation block MKT, a time-constantcalculation block TAU, a delay element calculation block DLY, a targetacceleration calculation block DDM, and a gain setting block KMTR.

In the target position calculation block MKT, based on a target pushingforce Fbt and a target pushing-force calculation characteristic(calculation map) CHmk, the target position (target rotation angle) Mktis calculated. The target position Mkt is a target value of the position(rotation angle) of the electric motor MTR. The calculation map CHmk,which corresponds to rigidities of the brake caliper CPR and thefriction members (brake pads) MSB, is pre-stored, as a non-linear“concave-down” characteristic, in the electronic control unit ECU.

In the time-constant calculation block TAU, based on the brakingoperation amount Bpa and a time-constant calculation characteristic(calculation map) CHτm, the time constant τm is calculated. As usedherein, the “time constant” is a parameter that is indicative of a speedof a response (how the output changes in response to the change of theinput) in the “delay element” to be detailed later. In a case where theoperation amount Bpa is less than a predetermined operation amount(predetermined value) bp1, the τm is calculated to be a firstpredetermined time constant (predetermined value) τ1(≧0). In a casewhere the Bpa is equal to or larger than the predetermined value bp1 andconcurrently is less than a predetermined value bp2, the τm iscalculated to sequentially increase from the first predetermined timeconstant τ1 to a second predetermined time constant τ2 depending on anincrease of the Bpa. In a case where the Bpa is equal to or larger thanthe predetermined amount bp2, the τm is calculated to be a secondpredetermined time constant (predetermined value) τ2 (>τ1).

Instead, it is possible to calculate the time constant τm based on acalculation characteristic (calculation map) CHτn. In the calculationmap CHτn, in a case where the Bpa is less than the predetermined valuebp1, the τm is calculated to be the predetermined value τ1 (≧0), whilein a case where the Bpa is equal to or larger than the predeterminedvalue bp1, the τm is calculated to be the predetermined value τ2 (>τ1).In each calculation characteristic CHτm or CHτn, when the brakingoperation amount Bpa is small, in order not to execute the delay elementbased calculation processing, the predetermined value τ1 may be set tobe “0”.

In the delay element calculation block DLY, based on the target positionMkt of the electric motor MTR, the target position (processed value) fMkthat is the result of the delay element based calculation processing. Indetail, the calculation processing that uses the delay element (e.g.,first-order delay element) that includes the time constant τmcorresponding to the response of the brake actuator BRK (i.e., theresponse of the electric motor MTR) is executed with respect to thetarget position (original value) Mkt of the electric motor, therebycalculating the post-delay process target position (processed value)fMk. By subjecting the Mkt to the delay processing, the response of thebrake actuator BRK is considered as a transfer function with the delayelement instead of the “gradient limitation”, allowing to calculate thetarget value fMk that corresponds to the response. In other words, theresponse of the BRK (how the temporal change amount of output varies inresponse to the temporal change amount of input to the system) isindicated by the transfer function with the delay element represented bythe time constant, and hence the fMk can be calculated by using thistransfer function. As used herein, the transfer function is a functionthat is indicative of a relationship between inputs to the system(control system) and their corresponding outputs, and the time constantis a parameter that is indicative of the response speed of the delayelement.

As the delay element, an n-th order delay element (n is an integer of“1” or more) is available. The delay element is represented in terms ofLaplace transformation and, for example, in a case of the first-orderdelay element, a transfer function G(s) is represented by the followingexpression (1).

G(s)=K/(τm·s+1)  (1),

where τm is a time constant, K is a constant, and s is Laplacianoperator.

In addition, in a case where the delay element is a second-order delayelement, the transfer function G(s) in the delay element calculation isrepresented by the following expression (2).

G(s)=K/{s·(τm·s+1)}  (2)

Moreover, in the delay element calculation, an idle time may beconsidered. The idle time is a time that is required until the outputbegins in response to the input. In such a case, the transfer functionG(s) that is indicative of the response of the BRK is represented by thefollowing expression (3) (delay element calculation using first-orderdelay and the idle time) or expression (4) (delay element calculationusing second-order delay and the idle time).

G(s)={K/(τm·s+1)}·e ^(L·s)  (3)

G(s)=[K/{s·(τm·s+1)6}]·e ^(−L·s)  (4)

where L is the idle time, and e is Napierian number (the base of naturallogarithms).

In the target acceleration calculation block DDM, based on thepost-delay process target position (processed value) fMk, the post-delayprocess target acceleration (processed acceleration value) ddfMK iscalculated. The ddfMk is a target value of the acceleration (angularacceleration) of the electric motor MTR. In detail, the ddfMk iscalculated by subjecting the fMk to second-order differentiation. TheddfMk is calculated to be a value with a plus sign during accelerationof the electric motor MTR (when starting from the stopped state), whilethe ddfMk is calculated to be a value with a minus sign duringdeceleration of the electric motor MTR (when intended to be stopped).

In the gain setting block KMTR, there is stored a coefficient (gain)k_mtr that is used in converting the post-delay process targetacceleration (processed acceleration value) ddfMk into the targetenergization amount of the electric motor. The coefficient k_mtrcorresponds to a value obtained by dividing the inertia (constant) j_mtrof the electric motor by the torque constant k_tq of the electric motor.Then, the inertia compensation control energization amount (targetvalue) Ijt or Ikt is calculated based on the ddfMk and the k_mtr. Indetail, each of the Ijt and the Ikt is calculated by multiplying theddfMk by the k_mtr.

In the inertia compensation control block INR of the above-mentionedfifth embodiment (see FIG. 9), the target position (unprocessed value)Mkt is calculated based on the target pushing force Fbt, and thepost-delay process target position (processed value) fMk is calculatedby subjecting the resultant Mkt to the delay processing (e.g.,first-order delay processing). Further, the target acceleration(processed acceleration value) ddfMk is calculated by subjecting the fMkto second-order differentiation, and the Ijt or Ikt is calculated basedon the resultant ddfMk. Instead of these calculations, the post-delayprocess target pushing force (processed value and concurrently processedtarget pushing force) fFb may be calculated by subjecting the targetpushing force (unprocessed value) Fbt to the delay processing, thetarget pushing-force acceleration (processed acceleration value) ddfFbmay be calculated by subjecting the fFb to second-order differentiation,and the inertia compensation energization amount Ijt or Ikt may becalculated based on the resultant ddfFb. In addition, the post-delayprocess operation amount (processed value) fBp may be calculated bysubjecting the Bpa to the delay processing, the operation acceleration(processed acceleration value) ddfBp may be calculated by subjecting theresultant fBp to second-order differentiation, and the inertiacompensation energization amount Ijt or Ikt may be calculated based onthe resultant ddfBp. In other words, in the inertia compensation controlblock INR, it is possible to calculate the processed value (value afterfilter processing) fBp, fFb, or fMk by subjecting the unprocessed value(Bpa, Fbt, or Mkt) that is calculated based on the operation amount Bpaof the braking operation member BP to the delay element calculation.Then, subjecting the processed value fBp, fFb, or fMk to second-orderdifferentiation calculates the processed acceleration value (equivalentto the acceleration obtained by subjecting the processed value tosecond-order differentiation) ddfBp, ddfFb, or ddfMk, and the inertiacompensation energization amount Ijt or Ikt is calculated based on theresultant processed acceleration value ddfBp, ddfFb, or ddfMk.

The torque that compensates for the inertia of the electric motor is inproportion to its rotation angular acceleration. For this reason, it isnecessary to adequately calculate the rotation angular acceleration (orits equivalent value) of the electric motor in order to adequatelyperform the inertia compensation. In view of this, in theabove-mentioned fifth embodiment, the response of the electric motor MTRis taken into consideration as the transfer function with the delayelement using the time constant, instead of the “gradient limitation”.In detail, an original state amount of any one of the unprocessed valuesBpa, Fbt, and Mkt that are calculated based on the Bpa is subjected tocalculation using a delay element (e.g., first-order delay element)having a time constant τm (time until the output reaches about 63.2% ofthe target value in response to a step input) corresponding to theresponse of the electric motor MTR, thereby calculating the processedvalue fBp, fFb, or fMk. Then, based on the resultant processed valuefBp, fFb, or fMk, the processed acceleration value (equivalent to theacceleration obtained by subjecting the processed value to second-orderdifferentiation) ddfBp, ddfFb, or ddfMk is calculated, to therebyadequately calculate the inertia compensation control target value Ijtor Ikt.

In the above-mentioned time-constant calculation block TAU, the timeconstant τm is calculated as a variable value based on the brakingoperation amount Bpa or the like. However, the time constant τm may becalculated as a predetermined value (fixed value).

FIG. 10 is a diagram corresponding to time T (time-series diagram) fordescribing operations and effects of the inertia compensation controlblock INR of the above-mentioned fifth embodiment. The brake actuatorBRK that includes the electric motor MTR and other equipment isrepresented in terms of the transfer function (delay elementcalculation), and the time constant τm is employed as an indicator forindicating the speed of the response thereof. The target position(target rotation angle) Mkt is subjected to the calculation processing(delay processing) using the delay element with the τm, therebycalculating the post-process target position fMk. The post-processtarget acceleration ddfMk is calculated by subjecting the post-processtarget position fMk to second-order differentiation, and the ddfMk isconverted into the energization amount for calculating the Ijt or Ikt.The response of the electric motor MTR is indicated by the transferfunction in which the time constant τm is set instead of the “gradientlimitation”. Therefore, the target value of the energization amount tothe electric motor MTR is adequately calculated at its starting-up (inthe vicinity of time t0) or before its stopping (in the vicinity of timet1). As a result, the inertia compensation control is allowed to beexecuted in an adequate manner. Thus, the responsiveness of the electricmotor MTR can be ensured and the overshoot can be suppressed.

In the preceding descriptions, the target position Mkt is subjected tothe delay element based calculation processing. However, it is possibleto subject at least one state amount among the operation amount Bpa, thetarget pushing force Fbt, and the target position Mkt to the delayelement based calculation processing (delay processing). In addition,calculating the τm in the time-constant calculation block TAU uses theoperation amount Bpa. However, it is possible to employ at least oneoriginal state amount (state amount before delay element basedcalculation processing) among the operation amount Bpa, the targetpushing force Fbt, and the target position Mkt. Even in such a case,similarly to the above, it is possible to use the calculation map τm orτn.

<Configuration of Inertia Compensation Control Block of SixthEmbodiment>

Next, with reference to FIG. 11, the inertia compensation control blockINR according to a sixth embodiment of the present invention isdescribed. As illustrated in FIG. 11, in the INR of the sixthembodiment, it is determined, based on the operation amount Bpa, whetheror not the motion state of the electric motor MTR is in an “accelerationstate,” when the acceleration state is determined, the delay elementcalculation is not executed, while only when the acceleration state isnot determined, the delay element calculation is executed.

The inertia compensation control block INR includes a target positioncalculation block MKT, a time-constant calculation block TAU, a delayelement calculation block DLY, an acceleration state determinationcalculation block FLA, a selection calculation block DDM, a targetacceleration calculation block DDM, and a gain setting block KMTR. Thetarget position calculation block MKT, the time-constant calculationblock TAU, the delay element calculation block DLY, and the targetacceleration calculation block DDM are the same as those in the INR ofthe fifth embodiment (see FIG. 9) and thus the detailed descriptionsthereof are omitted.

In the acceleration state determination calculation block FLA, based onthe operation amount Bpa of the braking operation member, it isdetermined whether or not the motion state of the electric motor MTRwhich corresponds to the operation is the acceleration state. In detail,based on the operation amount Bpa, the acceleration (unprocessedacceleration value) ddBp of the braking operation is calculated, andwhen the resultant ddBp is equal to or larger than a predeterminedacceleration (predetermined value) ddb0 (ddBp≧ddb0), it is determined to“be in the acceleration state (acceleration state)”. On the other hand,when the resultant ddBp is less than the predetermined acceleration(predetermined value) ddb0 (ddBp<ddb0), it is determined to “not be inthe acceleration state (out-of-acceleration state)”. From theacceleration state determination calculation block FLA, a determinationflag FLa is output, which is indicative of the determined result.Regarding the determination flag FLa, its value “1” is indicative of the“acceleration state”, while its value “0” is indicative of the“out-of-acceleration state”.

In the selective means SNV, based on the acceleration statedetermination flag FLa, any one of the target position (processed value)fMk which is obtained after being processed by the delay elementcalculation and the target position (unprocessed value) Mkt which is notprocessed by the delay element calculation is determined (selected). Inthe selection calculation block SNV, in a case of FLa=1 (accelerationstate), the target position (pre-process target position) Mkt which isnot processed by the delay element calculation is selected, while in acase of FLa=0 (out-of-acceleration state), the target position(post-process target position) fMk obtained after being processed by thedelay element calculation is selected.

In the target acceleration calculation block DDM, the second-orderdifferentiation is performed based on the target position (one ofunprocessed values) Mkt obtained without the delay element calculationor the target position (one of processed values) fMk obtained via thedelay element calculation. Then, a target acceleration ddMk or ddfMk iscalculated which corresponds to one of the target positions Mkt and fMk.Here, the ddMk and the ddfMk are the target values of the acceleration(angular acceleration) of the electric motor MTR. Here, the unprocessedtarget acceleration ddMk obtained without the delay element calculationis calculated during acceleration (when starting from the stopped state)of the electric motor MTR and is thus assigned with a plus sign. On theother hand, the post-process target acceleration ddfMk obtained via thedelay element calculation is calculated during deceleration (whenintended to be stopped) of the electric motor MTR and is thus assignedwith a minus sign.

In the gain setting block KMTR, there is stored a coefficient (gain)k_mtr that is used for converting the target acceleration ddMk(unprocessed acceleration value) or ddfMk (processed acceleration value)into the energization amount. The k_mtr corresponds to a value obtainedby dividing the inertia (constant) j_mtr of the electric motor by thetorque constant k_tq of the electric motor. Then, based on the ddfMk andthe k_mtr, the inertia compensation energization amount (target value)Ijt or Ikt is calculated.

In a case where the “acceleration state” is determined (FLa=1), based onthe target acceleration obtained without the delay element calculation(target acceleration calculated based on unprocessed value orunprocessed acceleration value) ddMk and the k_mtr, Ijt=ddMK×k_mtrallows to calculate the during-acceleration inertia compensationenergization amount Ijt. In other words, the during-acceleration inertiacompensation energization amount Ijt is calculated based on theunprocessed value that is obtained without the delay elementcalculation.

On the other hand, in a case where the “acceleration state” is notdetermined (FLa=0), based on the target acceleration obtained via thedelay element calculation (target acceleration calculated based onprocessed value or processed acceleration value) ddfMk and the k_mtr,Ikt=ddfMK×k_mtr allows to calculate the during-deceleration inertiacompensation energization amount Ikt. In other words, theduring-deceleration inertia compensation energization amount Ikt iscalculated based on the processed value obtained via the delay elementcalculation.

In the sixth embodiment, based on any one state amount of the targetposition (unprocessed value) Mkt calculated based on the target pushingforce Fbt and the fMk (processed value) obtained by subjecting the Mktto the delay processing, the target acceleration (ddMk or ddfMk) iscalculated to calculate the inertia compensation energization amount Ijtor Ikt. Instead, as the original state amount (original value) forcalculating the Ijt or Ikt, it is possible to employ at least one stateamount among the operation amount Bpa, the target pushing force Fbt, andthe target position Mkt.

In a case where the target pushing force Fbt is used as the originalvalue, the processed target pushing force fFb is calculated, and basedon the determination flag FLa, the selection calculation block SNVselects any one of the unprocessed target pushing force Fbt and theprocessed target pushing force fFb. Then, the selected target pushingforce (Fbt or fFb) is subjected to second-order differentiation forcalculating the target pushing-force acceleration value (ddFb or ddfFb),and based on the resultant target pushing-force acceleration value, theinertia compensation energization amount Ijt or Ikt is calculated.

In a case where the operation amount Bpa is used as the original stateamount, the processed operation amount fBp is calculated, and based onthe determination flag FLa, the selection calculation block SNV selectsany one of the unprocessed operation amount Bpa and the processedoperation amount fBp. Then, the selected operation amount (Bpa or fBp)is subjected to second-order differentiation for calculating theoperation amount acceleration value (ddBp or ddfBp), and based on theresultant operation amount acceleration value, the inertia compensationenergization amount Ijt or Ikt is calculated.

According to the sixth embodiment, in a case where the motion state ofthe electric motor MTR is the acceleration state, theduring-acceleration inertia compensation energization amount Ijt iscalculated by bypassing the delay element calculation, and hence theresponsiveness of the pushing force can be improved. In addition, in acase where the motion state of the electric motor MTR is theout-of-acceleration state, the during-deceleration inertia compensationenergization amount Ikt is calculated by involving therein an executionof the delay element calculation, and hence the overshoot of the pushingforce is suppressed with reliability, thereby improving the convergence.

<Configuration of Inertia Compensation Control Block of SeventhEmbodiment>

Next, with reference to FIG. 12, an inertia compensation control blockINR according to a seventh embodiment of the present invention isdescribed. In the above-mentioned INRs of the fifth and sixthembodiments (see FIG. 9 and FIG. 11), based on the acceleration value(the ddfMk or the like), the Ijt and the Ikt are calculated. Instead, inthe INR of the seventh embodiment, based on the acceleration valueddfBp, ddfFb, or ddfMk after being executed in the delay elementcalculation, it is determined whether or not the inertia compensationcontrol is necessary, and when the inertia compensation control isdetermined to be necessary, based on the preset pattern characteristic,calculating the inertia compensation energization amount Ijt, Ikt becomepossible.

The inertia compensation control block INR includes a time-constantcalculation block TAU, a delay element calculation block DLY, anoperation acceleration calculation block DDF, an inertia compensationcontrol necessity determination control block FLG, and an inertiacompensation control energization calculation block IJK.

The time-constant calculation block TAU and the delay elementcalculation block DLY are the same as those of the above-mentioned INRaccording to the fifth embodiment (see FIG. 9) and thus descriptionsthereof are omitted. In the delay element calculation block DLY, anafter-delay-element processing operation amount (processed value) fBp iscalculated based on the delay element calculation that takes intoconsideration of the operation amount Bpa and the time constant τm (thatcorresponds to the transfer function of the power derived from the brakeactuator BRK).

In the operation acceleration calculation block DDF, the processedoperation amount fBp is subjected to second-order differentiation,thereby calculating a processed operation acceleration (processedacceleration value) ddfBp. In detail, an after-delay-element processingoperation amount fBp is differentiated to calculate an operation speed(processed speed value) dfBp and then the dfBp is differentiated tocalculate the operation acceleration (processed acceleration value)ddfBp.

In the control necessity determination block FLG, it is determinedwhether or not an execution of the inertia compensation control isnecessary. In the control necessity determination calculation block FLG,a necessity determination flag FLj is calculated and output whichindicates a determination result of whether or not the inertiacompensation control during acceleration is necessary, and a necessitydetermination flag FLk is calculated and output which indicates adetermination result of whether or not the inertia compensation controlduring deceleration is necessary. Each of the necessity determinationflags FLj and FLk is indicative of “1” in a case of “necessary state ofcontrol” and is indicative of “0” in a case of “unnecessary state ofcontrol”.

The flag FLj that is indicative of the determination result regardingthe during-acceleration control is set to be “0 (unnecessary state ofcontrol)” in a case where the braking operation is not performed.Pursuant to the calculation map DFLj, at a time point when the ddfBpexceeds the first predetermined acceleration (predetermined value)ddb1(>0), the necessity determination flag FLj is switched from “0(unnecessary state)” to “1 (necessary state)” (FLj←1). Thereafter, whenthe ddfBp becomes less than the predetermined acceleration ddb2(<ddb1),the FLj is switched from “1” to “0”.

Pursuant to the calculation map DFLk, at a time point when the ddfBp isless than the second predetermined acceleration (predetermined value)ddb3(<0), the necessity determination flag FLk is switched from “0(unnecessary state)” to “1 (necessary state)” (FLk←1). Thereafter, whenthe ddfBp becomes not less than the predetermined acceleration(predetermined value) ddb4 (>ddb3, <0), the FLk is switched from “1” to“0”.

In the inertia compensation control energization amount calculationblock IJK, the during-acceleration and during-deceleration inertiacompensation energization amounts (target values) Ijt, Ikt arecalculated.

Based on the control flag FLi that is indicative of the necessitydetermination result of the during-acceleration inertia compensationcontrol and the during-acceleration control amount characteristic (firstcontrol amount characteristic and being in correspondence with the firstpattern) CHj, the during-acceleration inertia compensation energizationamount (first inertia compensation energization amount) Ijt iscalculated. The during-acceleration control amount characteristic CHj isin advance stored in the ECU as the characteristic (calculation map) ofthe Ijt relative to an elapsed time T since the during-accelerationinertia compensation control is determined to be necessary. In the CHj,the Ijt increases abruptly from “0” to a predetermined energizationamount (predetermined value) ij1 along with time from the time T of “0”and thereafter decreases gently from the predetermined energizationamount (predetermined value) ij1 to “0” along with time. In detail, inthe CHj, a time period tup that is required for the Ijt to increase from“0” to the predetermined energization amount ij1 is set to be shorterthan a time period tdn that is required for the Ijt to decrease from thepredetermined energization amount ij1 to “0”.

As illustrated in FIG. 12 with broken lines, in a case where theenergization amount increases, it is possible to set the Ijt, which hasa “concave-down” characteristic, so as to first increase abruptly andthereafter increase gently. On the other hand, in a case where theenergization amount decreases, it is possible to set the Ijt, which hasa “concave-up” characteristic, so as to first increase abruptly andthereafter decrease gently. Then, the time point when the necessitydetermination flag FLj is switched from “0 (unnecessary state)” to “1(necessary state)” is defined as an original time point (T=0) of theelapsed time in the CHj, and the inertia compensation energizationamount during acceleration of the electric motor (first inertiacompensation energization amount) Ijt is determined based on the elapsedtime T measured from the switched time point and the during-accelerationcontrol amount characteristic CHj. Even though the FLj is switched from“1” to “0” in the calculation of Ijt, the Ijt keeps being calculatedover a continuation duration that is set in the calculation map CHj. Itis to be noted that the Ijt is calculated as a positive value and isadjusted to increase the energization amount to the electric motor MTR.

The during-deceleration inertia compensation energization amount (secondinertia compensation energization amount) Ikt is calculated based on thedetermination flag FLk that indicates the necessity determination resultof inertia compensation control during the deceleration, and theduring-deceleration control amount characteristic (that is a secondcontrol amount characteristic and corresponds to the second pattern)CHk. The during-deceleration control amount characteristic CHk is storedin advance in the ECU as the characteristic (calculation map) of the Iktrelative to an elapsed time T since the during-deceleration inertiacompensation control is determined to be necessary. In the CHk, the Iktdecreases abruptly from “0” to a predetermined energization amount(predetermined value) ik1 along with time from the time T of “0” andthereafter increases gently from the predetermined energization amount(predetermined value) ik1 to “0” along with time. In detail, in the CHk,a time period tvp that is required for the Ikt to decrease from “0” tothe predetermined energization amount ik1 is set to be shorter than atime period ten that is required for the Ikt to increase from thepredetermined energization amount ik1 to “0”.

As illustrated in FIG. 12 with broken lines, in a case where theenergization amount decreases, it is possible to set the Ikt, which hasa “concave-up” characteristic, so as to first decrease abruptly andthereafter decrease gently. On the other hand, in a case where theenergization amount increases, it is possible to set the Ikt, which hasa “concave-down” characteristic, so as to first increase abruptly andthereafter increase gently. Then, the time point when the necessitydetermination flag FLk is switched from “0” to “1” is defined as anoriginal time point (T=0) in the CHk for measuring an elapsed, and theinertia compensation energization amount during deceleration of theelectric motor (second inertia compensation energization amount) Ikt isdetermined based on the elapsed time T measured from the switched timepoint and the during-deceleration control amount characteristic CHk.Even though the flag FLk is switched from “1” to “0” in the calculationof the Ikt, the Ikt keeps being calculated over a continuation durationthat is set in the calculation map CHk. It is to be noted that the Iktis calculated as a negative value and is adjusted to decrease theenergization amount to the electric motor MTR.

Here, the calculation characteristic CHj (first pattern) in theduring-acceleration inertia compensation control and the calculationcharacteristic CHk (second pattern) in the during-deceleration inertiacompensation control are determined based on the maximum response fromthe braking means (brake actuator) BRK. In response to the changing ofthe input (target energization amount) to the BRK, the resultant output(displacement of the electric motor) occurs with a delay. The maximumresponse from the BRK (the maximum achievable state of the BRK inresponse to the input) means that a response from the MTR when providinga step input to the electric motor MTR (how the temporal change amountof the output changes in response to the temporal change amount of theinput). In other words, how the actual displacement (rotation angle) Mkachanges when the MTR is supplied with a predetermined targetenergization amount Imt as a step input (in an increasing direction fromzero). As illustrated in FIG. 13, similarly to the above-mentioned FIG.5, in a case where the electric motor MTR is supplied with the(predetermined) target energization amount as a step input (thus, thetarget value Mkt of the rotation angle (which is of the predeterminedamount mksO) is provided as a step input), the actual value (output) Mkaof the rotation angle changes to achieve the target value (input) Mkt(to follow the target value with a delay). The CHj and the CHk aredetermined based on the change of the Mka.

The torque that compensates for the inertia of the entire device(particularly, the inertia of the electric motor) is in proportion tothe rotation angular acceleration of the electric motor. Inconsideration of this fact, for achieving the inertia compensationproperly, the inertia compensation energization amount is calculatedbased on the actual acceleration (rotation angular acceleration) ddMkaof the electric motor. For this reason, the acceleration (rotationangular acceleration) ddMka is calculated by finding the second-orderdifferentiation of the actual displacement (rotation angle) Mka of theMTR and based on the resultant ddMka, the CHj and CHk are determined.For example, it is possible to set the first pattern CHj and the secondpattern CHk by multiplying the ddMka with a coefficient K (constantvalue).

In the CHj, the increase gradient of the Ijt upon abrupt increasethereof (the gradient of the Ijt relative to time) is determined basedon the maximum value or the average value of the increase gradient ofthe ddMka (the gradient of the ddMka that increases relative to time)between a time t1 when the step input starts and a time t2 when therotation angular acceleration ddMka reaches its maximum value ddm1. Onthe other hand, the decrease gradient of the Ijt upon gentle decreasethereof (the gradient of the Ijt relative to time) is determined basedon the maximum value or the average value of the decrease gradient ofthe ddMka (the gradient of the ddMka that decreases relative to time)between the time t2 when the ddMka reaches its maximum value ddm1 and atime t3 when the ddMka reaches almost zero.

In addition, in a case where the energization amount increases based onthe ddMk at the maximum response (step response) (based on the change ofddMka between time t1 and time t2), it is possible to set the CHj sothat the Ijt, which has a “concave-down” characteristic, first increasesabruptly and thereafter increases gently. Similarly, in a case where theenergization amount decreases based on the ddMka at the maximum response(based on the change of ddMka between time t2 and time t3), it ispossible to set the CHj so that the Ijt, which has a “concave-up”characteristic, first decreases abruptly and thereafter decreasesgently.

In the CHk, the decrease gradient of the Ikt upon abrupt decreasethereof (the gradient of the Ikt relative to time) is determined basedon the minimum value or the average value of the decrease gradient ofthe ddMka (the gradient of the ddMka that decreases relative to time)between a time t4 when the ddMka begins to decrease from zero and a timet5 when the ddMka reaches its minimum value ddm2. On the other hand, theincrease gradient of the Ikt upon gentle increase thereof (the gradientof the Ikt relative to time) is determined based on the maximum value orthe average value of the increase gradient of the ddMka (the gradient ofthe ddMka that increases relative to time) between the time t5 when theddMka reaches its minimum value ddm2 and a time t6 when the ddMkareturns almost zero.

In addition, in a case where the energization amount decreases based onthe ddMka at the maximum response (step response) (based on the changeof ddMka between time t4 and time t5), it is possible to set the CHk sothat the Ikt, which has a “concave-up” characteristic, first decreasesabruptly and thereafter decreases gently. Similarly, in a case where theenergization amount increases based on the ddMka at the maximum response(based on the change of ddMka between time t5 and time t6), it ispossible to set the CHk so that the Ikt, which has a “concave-down”characteristic, first increases abruptly and thereafter increasesgently.

In a case where the electric motor MTR is in acceleration (particularly,when the MTR is initiated), generating torque is required for overcomingthe frictions of the bearings and the like, while in a case where theelectric motor MTR is in deceleration (particularly, when the MTR isstopping), the frictions act the MTR to decelerate. For this reason, theabsolute value of the during-acceleration predetermined energizationamount (the first predetermined energization amount) ij1 is set to belarger than the absolute value of the during-deceleration predeterminedenergization amount (the second predetermined energization amount) ik1(|ij1>|ik1|).

<Configuration of Inertia Compensation Control Block of EighthEmbodiment>

Next, with reference to FIG. 14, an inertia compensation control blockaccording to an eighth embodiment of the present invention is described.In the above-mentioned INR according to the seventh embodiment (see FIG.12), the during-acceleration determination calculation block FLJ of thecontrol necessity determination control block FLG determines, based onthe processed acceleration value (ddfBp or the like), whether or not theinertia compensation control is necessary during the acceleration. Tothe contrary, this INR according to the eighth embodiment determines,based on the unprocessed speed value (dBP or the like) as an alternativeof the processed acceleration value (ddfBp or the like), whether or notthe inertia compensation control is necessary during the acceleration.The following description of the eighth embodiment deals only with thedifference from the above-mentioned seventh embodiment (see FIG. 12).

In the operation speed calculation block DBP, based on the operationamount Bpa of the braking operation member, its operation speed(unprocessed speed value) dBp is calculated. The operation speed bBp iscalculated by subjecting the Bpa to first-order differentiation.

In the during-acceleration determination calculation block FLJ of thecontrol necessity determination calculation block FLG, based on theoperation speed dBp of the braking operation member BP, it is determinedwhether the inertia compensation control is in “necessary state (statein necessity of executing the control)” or in “unnecessary state(without necessity of executing control).” The determination result isoutput as the necessity determination flag (control flag) FLj. “0” and“1” of the necessity determination flag Flj correspond to “unnecessarystate” and “necessary state”, respectively. It is to be noted that thedetermination flag FLj is set to be “0” as an initiative value in a casewhere the braking operation is not performed.

Based on the operation speed dBp of the braking operation member, it isdetermined whether or not the inertia compensation control is necessaryduring acceleration (e.g., when the rotation speed of the electric motorincreases). In detail, pursuant to the calculation map CFLj, at a timepoint when the dBp exceeds the predetermined operation speed(predetermined value) db1, the during-acceleration necessitydetermination flag Flj is switched from “0 (unnecessary state)” to “1(necessary state)” (FLj←1). Thereafter, at a time point when the dBp isless than the predetermined operation speed (predetermined value) db2,the necessity determination flag FLj is switched from “1” to “0”(FLj←0).

For determining the necessity of the inertia compensation control, otherthan the operation speed dBp, the operation amount Bpa of the brakingoperation member is available. In such a case, at a time point when theBpa exceeds the predetermined operation amount (predetermined value) bp1and concurrently the dBp exceeds the predetermined operation speed(predetermined value) db1, the necessity determination flag FLj isswitched from “0” to “1”. The use of the condition of Bpa>dp1 as adetermination criteria can compensate for the influences of the noiseand other factors in the dBp, thereby enabling a reliable determination.

In the eighth embodiment, for the necessity determination in theduring-acceleration determination calculation block FLJ, the dBp isused. However, it is possible to use at least one of the dBp, the dFb,and the dMk. The target pushing-force speed dFb is calculated bydifferentiating the target pushing force Fbt. In addition, the targetspeed dMk is calculated by differentiating the target position Mkt. Eachof the target pushing force Fbt and the target position Mkt is aunprocessed value that is not subjected to the delay element processingin the delay element calculation block DLY.

Determining the during-acceleration control based on the processedacceleration value (ddfBp or the like) that is subjected to the delayelement calculation brings in a disadvantage from the viewpoint ofresponsiveness. Thus, in the fourth embodiment, in theduring-acceleration inertia compensation control for which theresponsiveness is required, the necessity of control is determined usingthe state amount (unprocessed value) that is not subjected to the delayprocessing. On the other hand, in the during-deceleration control,determining the necessity of control based on the processed accelerationvalue (ddfBp or the like) makes it possible to attain an overshootsuppression with reliability.

Now, descriptions are made as to operations and effects of the inertiacompensation control in the inertia compensation control block INR whichare common to the above-mentioned fifth to eighth embodiments. Theinertia compensation control is a control for adjusting the energizationamount (Ijt, Ikt) relative to the target energization amount Imt, theenergization amount (Ijt, Ikt) corresponding to the force (torque) thatis necessary for the moving parts (including the MTR) of the devicehaving the inertia to accelerate or decelerate. In detail, theenergization amount is compensated for (corrected) by increasing thetarget energization amount during acceleration of the electric motor,while the energization amount is compensated for (corrected) bydecreasing the target energization amount during deceleration of theelectric motor.

In order to ensure the responsiveness of the braking torque duringacceleration of the electric motor MTR (particularly, at itsinitiation), it is important to improve the start-up of the electricmotor MTR (motion initial stage from at rest) by compensating for theinfluences of the inertia of the electric motor and static frictions ofthe bearings and the like. According to the above-mentioned fifth toeighth embodiments, the actual response (how the output changes inresponse to the change of the input) of the braking means is representedbased on the delay element (n-th delay transfer function, where nrepresents an integer of “1” or more) using the “time constant (fixedvalue or variable calculated based on the Bpa) instead of the “gradientlimitation” discussed in BACKGROUND ART. Thus, it is possible tocalculate the inertia compensation current immediately after theelectric motor begins to accelerate with reliability (see FIG. 10).Thus, it is possible to compensate for the influences of the inertia ofthe electric motor and the like, resulting in a remarkable improvementof the responsiveness of the braking torque when the electric motorbegins to rotate.

Likewise, during deceleration of the electric motor (in the case of thetransfer from motion state to rest state of the electric motor), it isalso important to compensate for the inertia at the initial stage of thedeceleration of the electric motor. According to the above-mentionedfifth to eighth embodiments, the actual response (how the output changesin response to the change of the input) of the braking means isrepresented based on the delay element (n-th delay transfer function,where n represents an integer of “1” or more) using the “time constant(fixed value or variable calculated based on the Bpa)” instead of the“gradient limitation” discussed in BACKGROUND ART. Thus, it is possibleto calculate the inertia compensation current immediately after theelectric motor begins to decelerate with reliability (see FIG. 10).Thus, it is possible to increase the deceleration of the electric motorimmediately after the electric motor begins to decelerate, resulting ina remarkable suppression of the overshoot of the braking torque. Insummary, with the preceding configuration, it is possible to compensatefor the influences of the inertia of the entire device which includesthe inertia of the electric motor with efficiency and with reliability.

1. A vehicle brake control device, comprising: operation amountacquisition means for acquiring an operation amount of a driver-operatedbraking operation member of a vehicle; braking means for causing anelectric motor to generate a braking torque to a wheel of the vehicle;and control means for calculating a target energization amount based onthe operation amount and controlling the electric motor based on thetarget energization amount, wherein the control means is configured to:determine, based on the operation amount, whether or not an inertiacompensation control for compensating for an influence of an inertia ofthe braking means is necessary; calculate, in a case where the inertiacompensation control is determined to be necessary, an inertiacompensation energization amount for compensating for the influence ofthe inertia of the braking means based on a time-series pattern that isset in advance based on a maximum response from the braking means; andcalculate the target energization amount based on the inertiacompensation energization amount.
 2. A vehicle brake control deviceaccording to claim 1, wherein the control means is configured to:determine, based on the operation amount, whether or not the inertiacompensation control is necessary during acceleration of the electricmotor in which a rotation speed thereof increases; and use, in a casewhere the inertia compensation control during the acceleration isdetermined to be necessary, as the time-series pattern, a first patternin which the inertia compensation energization amount increases fromzero at an increase gradient and thereafter decreases to zero at adecrease gradient, the increase gradient being set in advance based onan actual position change of the electric motor that occurs when a stepinput of the target energization amount is performed to the electricmotor, the decrease gradient being set in advance to be gentler than theincrease gradient.
 3. A vehicle brake control device according to claim1, wherein the control means is configured to: determine, based on theoperation amount, whether or not the inertia compensation control isnecessary during deceleration of the electric motor in which a rotationspeed thereof decreases; and use, in a case where the inertiacompensation control during the deceleration is determined to benecessary, as the time-series pattern, a second pattern in which theinertia compensation energization amount decreases from zero at adecrease gradient and thereafter increases to zero at an increasegradient, the decrease gradient being set in advance based on an actualposition change of the electric motor that occurs when a step input ofthe target energization amount is performed to the electric motor, theincrease gradient being set in advance to be gentler than the decreasegradient.
 4. A vehicle brake control device according to claim 1,wherein the control means is configured to: determine, based on theoperation amount, whether or not the inertia compensation control isnecessary during acceleration of the electric motor in which a rotationspeed thereof increases; and use, in a case where the inertiacompensation control during the acceleration is determined to benecessary, as the time-series pattern, a first pattern in which theinertia compensation energization amount increases from zero at anincrease gradient and thereafter decreases to zero at a decreasegradient, the increase gradient being set in advance based on an actualposition change of the electric motor that occurs when a step input ofthe target energization amount is performed to the electric motor, thedecrease gradient being set in advance to be gentler than the increasegradient; determine, based on the operation amount, whether or not theinertia compensation control is necessary during deceleration of theelectric motor in which a rotation speed thereof decreases; and use, ina case where the inertia compensation control during the deceleration isdetermined to be necessary, as the time-series pattern, a second patternin which the inertia compensation energization amount decreases fromzero at a decrease gradient and thereafter increases to zero at anincrease gradient, the decrease gradient being set in advance based onan actual position change of the electric motor that occurs when a stepinput of the target energization amount is performed to the electricmotor, the increase gradient being set in advance to be gentler than thedecrease gradient.
 5. A vehicle brake control device according to claim4, wherein the control means is configured to maintain the inertiacompensation energization amount at zero in a case where the electricmotor is in motion immediately before the inertia compensation controlduring the acceleration is determined to be necessary.
 6. A vehiclebrake control device according to claim 4, wherein the control means isconfigured to calculate the inertia compensation energization amountbased on the second pattern instead of the first pattern in a case wherethe inertia compensation control during the deceleration is determinedto be necessary in a period during which the inertia compensationenergization amount is calculated based on the first pattern.
 7. Avehicle brake control device according to claim 4, wherein the controlmeans is configured to maintain the inertia compensation energizationamount at zero in a case where the inertia compensation control duringthe deceleration is determined to be necessary in a state in which theinertia compensation control during the acceleration is not determinedto be necessary.
 8. A vehicle brake control device according to claim 2,wherein the control means is configured to use, as the first pattern, apattern in which the inertia compensation energization amount increasesfrom zero in a concave-down fashion and thereafter decreases to zero ina concave-up fashion.
 9. A vehicle brake control device according toclaim 3, wherein the control means is configured to use, as the secondpattern, a pattern in which the inertia compensation energization amountdecreases from zero in a concave-up fashion and thereafter increases tozero in a concave-down fashion.
 10. A vehicle brake control deviceaccording to claim 1, wherein the control means is configured to:calculate, based on the operation amount, an operation state variablethat corresponds to at least one of an operation acceleration or anoperation speed; and determine, based on the operation state variable,whether or not the inertia compensation control is necessary.
 11. Avehicle brake control device, comprising: operation amount acquisitionmeans for acquiring an operation amount of a driver-operated brakingoperation member of a vehicle; braking means for causing an electricmotor to generate a braking torque to a wheel of the vehicle; andcontrol means for calculating a target energization amount based on theoperation amount and controlling the electric motor based on the targetenergization amount, wherein the control means is configured to:calculate an inertia compensation energization amount for compensatingfor an influence of an inertia of the braking means based on a delayelement that has a time constant indicating a response from the brakingmeans and the operation amount; and calculate the target energizationamount based on the inertia compensation energization amount.
 12. Avehicle brake control device according to claim 11, wherein the controlmeans is configured to determine the time constant to have a relativelylarger value as the operation amount becomes larger.
 13. A vehicle brakecontrol device according to claim 11, wherein the control means isconfigured to: calculate a processing value based on the delay elementand the operation amount; calculate an acceleration equivalent value bysubjecting the processing value to second-order differentiation; andcalculate the inertia compensation energization amount based on theacceleration equivalent value.
 14. A vehicle brake control deviceaccording to claim 13, wherein the control means is configured to:calculate a first kind of the inertia compensation energization amountfor increasing the target energization amount based on a firsttime-series pattern set in advance in a case where the accelerationequivalent value exceeds a first predetermined acceleration; andcalculate a second kind of the inertia compensation energization amountfor decreasing the target energization amount based on a secondtime-series pattern set in advance in a case where the accelerationequivalent value is less than a second predetermined acceleration.
 15. Avehicle brake control device according to claim 13, further comprisingenergization amount acquisition means for acquiring an actualenergization amount to the electric motor, wherein the control means isconfigured to: calculate, in a case where the acceleration equivalentvalue exceeds a first predetermined acceleration, a first kind of theinertia compensation energization amount for increasing the targetenergization amount based on a first time-series pattern set in advance,and acquire time-series data that corresponds to the first pattern basedon the actual energization amount acquired in correspondence to thefirst kind of the inertia compensation energization amount; andcalculate a second kind of the inertia compensation energization amountfor decreasing the target energization amount based on the time-seriesdata in a case where the acceleration equivalent value is less than asecond predetermined acceleration.
 16. A vehicle brake control deviceaccording to claim 11, wherein the control means is configured to:determine, based on the operation amount, whether or not the brakingoperation member is in an acceleration state in which an operation speedthereof increases; and avoid executing calculation processing that usesthe delay element in a case where the acceleration state is determined,and execute the calculation processing that uses the delay element in acase where the acceleration state is not determined.